# CBSE Class 12th Mathematics, Physics and Chemistry Solved Guess Papers: 2018

Solved Guess Papers for CBSE board exam 2018 are available here. These guess papers are available in the form of a combined package. This package is specially prepared for Maths and Science students who are going to appear for CBSE board exam 2018.

CBSE has recently released Class 12 date sheet. As per the date sheet, CBSE Class 12 board exams, 2018 will start from 5 March 2018 (English paper). Now, students don’t have much time for preparation. This is the time when students need to focus more on revision & practice rather than studying new topics.

Due to this reason, Jagranjosh.com has provided a complete package for the Class 12th students having Mathematics, Chemistry and Physics subjects. These papers are developed by subject experts after the brief analysis of previous 5 years’ papers.

After going through previous year papers, our subject experts learned that questions based on some important concepts are frequently asked in CBSE board exams, every year. These solved guess papers contain all such important concepts. These guess papers are also based on latest examination pattern. This package will be very helpful for the students preparing for CBSE board exam 2018.

**Important highlights of the complete package:**

- Total 3 eBooks are available in this package
- One eBook for each subject (Mathematics, Physics and Chemistry)
- Ideal to understand examination pattern & marking trends
- Strictly follows the CBSE marking scheme
- Focuses on the concepts which need the proper explanation
- Offers detailed explanation & solution for each and every question
- Helps in building student's confidence for the board exam
- Perfect for self-evaluation as well testing your exam preparedness

**CBSE Class 12 Sample Paper 2018: All Subjects**

**More details about the 3 Guess Papers included in this package:**

**Class 12th Maths Guess Paper**

- Question number 1 to 4 in Section A are very short-answer type questions carrying 1 mark each
- Question number 5 to12 in Section B are very short-answer type questions carrying 2 marks each
- Question number 13 to 23 in Section C are very long-answer-I type questions carrying 4 marks each
- Question number 24 to 29 in Section D are very long-answer-II type questions carrying 6 marks each

There is no overall choice is present in the paper. However, internal choices are present in some questions.

**Some questions from the solved Maths guess paper are given below:**

**Question:** Find whether the binary operation * on the set N of natural number defined by *x***y* = 2* ^{xy}* is associative or not

**Solution:**

(1*2) *3 = 2^{2}*3 = 2^{12}

1*(2*3) = 1*2^{6} = 2^{64}

Therefore, (1*2)*3 ≠ 1*(2*3)

**Question:** If the radius of an iron sphere is measured as 9 cm with an error if 0.03 cm, then calculate the approximate error in calculating its volume.

**Solution:**

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**Question:** Find the coordinates of the point where the line through (3, – 4, – 5) and (2, –3, 1) crosses the plane passing through three points (2, 2, 1), (3, 0, 1) and (4, –1, 0).

**Solution:**

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**Question: **Arun can solve 90 % of the problems given in a book whereas Amit can solve 70%. Find the probability that at least one of them will solve the problem, selected at random from the book?

**Solution:**

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**Question: **The monthly incomes of Aryan and Babban are in the ratio 3:4 and their monthly expenditures are in the ratio 5:7. If each saves Rs 15,000 per month, find their monthly incomes using matrix method.

**Solution:**

Suppose the monthly incomes of Aryan and Babban be 3*x* and 4*x* and their monthly expenditures are 5*y* and 7*y* respectively.

Since each saves Rs 15000 per month.

Monthly saving of Aryan: 3 *x* ‒ 5 *y* = 15,000 and monthly saving of Babban: 4 *x* ‒ 7 *y* = 15,000.

The above system of equations can be written in the matrix form as,

A X = B,

Where,

Therefore monthly income of Aryan = 3×30000= Rs.90,000.

Therefore monthly income of Babban = 4×30000= Rs.1,20,000.

**Question:** Prove that *f* (*x*) = | ln *x *| for* x *> 0 is not differentiable for all *x* > 0.

**Solution:**

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**Question:** A magazine seller has 500 subscribers and collects annual subscription charges of Rs.300 per subscriber. She proposes to increase the annual subscription charges and it is believed that for every increase of Re 1, one subscriber will discontinue. What increase will bring maximum income to her? Make appropriate assumptions in order to apply derivatives to reach the solution. Write one important role of magazines in our lives.

**Solution:**

Increase in subscription charges = Rs *x*, Decrease in the number of subscriber = *x*.

Obviously,* x* is a whole number.

Income is given by y = (500 – *x*) (300 + *x*). Let us assume for the time being

*y* is maximum when *x* = 100, which is a whole number. Therefore, she must increase the subscription charges by Rs 100 to have maximum income.

Magazines contribute, a great deal, to the development of our knowledge. Through valuable and subtle critical and commentary articles on culture, social civilization, new life style we learn a lot of interesting things. Through reading magazines, our mind and point of view are consolidated and enriched.

**CBSE Class 12 Syllabus 2017-2018: All Subjects**

**Question:** Find the general solution of 2*x dy* + (1 + tan *y*) (*dx* - *dy*) = 0.

**Solution:**

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**Question:** Find the point on the curve *y *= *x*^{3} ‒ 11*x *+ 5 at which the equation of tangent is *y *= *x *‒ 11.

**Solution:**

Given, *y *= *x*^{3} ‒ 11*x *+ 5 …(*i*)

**Question:** A company has two plants to manufacture scooters. Plants I manufactures 70% of the scooters and Plant II manufactures 30%. At Plant I, 80% if the scooters are rated as of standard quality and at Plant II, 90% of the scooters are rated as of standard quality. A scooter is chosen at random and is found to be of standard quality. Find the probability that it has come from plant II?** **

**Solution:**

Suppose *E*_{1}, *E*_{2} and *A* be the following events such that,

*E*_{1} = Plant I is chosen, *E*_{2} = Plant II is chosen and *A* = scooter is of standard quality

**Question:** Find the length of foot of perpendicular from the point (7, 14, 5) to the plane 2 *x* + 4 *y* – *z *= 2. Also, find the image of the point P in the line.

**Solution:**

Suppose *M* be the foot of the perpendicular from *P* on the plane 2 *x* + 4 *y* – *z* = 2.

So, *PM *is the normal to the plane.

Its direction ratios are 2, 4, –1.

As *PM* passes through P (7, 14, 5). Therefore, its equation is

**Question:** A company manufactures gold rings & chains. The total number of rings and chains manufactured per day is exactly 24. It takes 1 hour to make a ring and 30 minutes to make a chain. The maximum number of hours available per day is 16. If the profit on a ring is Rs. 300 and that on a chain is Rs 190, find the number of rings and chains that should be manufactured per day, so as to earn the maximum profit. Make it as an L.P.P. and solve it graphically.

**Solution:**

Total number of rings and chain manufactures per day = 24

Time taken in manufacturing ring = 1 hour

Time taken in manufacturing chain = 30 minutes or 1/2 hour

Number of hours available per day = 16

Maximum profit on ring = Rs. 300

Maximum profit on chain = Rs. 190

Let gold rings manufacture per day = *x*, chains manufactured per day =* y*

The above LPP can be stated mathematically as given below,

Maximize, Z = 300* x* + 190 *y*

*Subject to*

**
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At (16, 0): Z = 4800 + 0 = 4800

At (8, 16): Z = 2400 + 3040 = 5400 [Maximum]

At (8, 16): Z = 0 + 4560 = 4560

So, Z is maximum at (8, 16). Therefore, 8 gold chain and 16 chains must be manufactured per day to earn the maximum profit.

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**Other questions and solutions are available in the eBook (link to access the file is given at the end)**

**Class 12th Physics Guess Paper:**

In this Class 12th Physics ssolved Guess Paper, there are 5 sections (i.e., Section A, Section B, Section C, Section D and Section E)

- Section A contains question number 1 to 5 (very Short Answer type questions of one mark each)
- Section B contains question number 6 to 10 (Short Answer type I questions of two marks each)
- Section C contains question number 11 to 22 (Short Answer type II questions of three marks each)
- Section D contains question number 23 (value Based Question of four marks)
- Section E contains question number 24 to 26 (Long Answer type questions of five marks each)

Internal choices are present in short answer types questions and long answer type questions (According to latest CBSE Class 12 Physics Examination Pattern 2017 – 2018)

**Some questions from the solved Physics guess paper are given below:**

**Question: **Why is soft iron core preferred for making the core of a transformer?

**Answer:**

As, the area of hysteresis loop for soft iron is very small so, energy dissipated per unit volume per cycle of magnetisation is small.

**Question: **Write two ways by which the range of transmission can be increased?

**Answer:**

Range of transmission of T.V. signal can be increase

• By increasing the power of transmitting signal from TV station

• By increasing the heights of transmitting and receiving antenna

**Question: **What is meant by ‘half-life’ of a radioactive element? What percentage of a given mass of a radioactive substance will be left undecayed after four half lives?

**Answer:**

The time interval in which the number of atoms of a radioactive element decays to one-half of its initial value is called half-life of the element.

If *N _{o}* is the initial quantity of radioactive element, then the quantity

*N*of the element left after n half-live is given by: N =

*N*(1/2)

_{o}^{n}.

The amount of substance left after 4 half lives can be given as:

*N *= *N _{o}*(1/2)

^{4}=

*N*/16 or 6.25% of initial value.

_{o}**Question:**

Arrange the following electromagnetic radiations in ascending order of their frequencies:

(i) Microwaves

(ii) Radio waves

(iii) X-rays

(iv) Gamma rays

Write two uses of any two of these.

**Answer:**

Given electromagnetic radiations in ascending order of their frequencies are: Radio waves, microwaves, ultraviolet rays, X-rays and gamma

rays.

Uses of Electromagnetic Spectrum

(*i*) Gamma-rays are highly penetrating. They can penetrate thick iron blocks. Due to high energy, they are used to produce nuclear reactions. g-rays are produced in nuclear reactions. In medicine, they are used to destroy cancer cells.

(*ii*) X-rays are used in medical diagnostics to detect fractures in bones, tuberculosis of lungs,

presence of stone in gallbladder and kidney. They are used in engineering to check flaws in

bridges. In physics X-rays are used to study crystal structure.

**Question:** Amit is a resident of Tamil Nadu was all set to leave everything and shift to another place in view of the decision of Government to start nuclear thermal power plant at Tamil Nadu. His granddaughter Rashi, a science student was really upset on the ignorant decision of her grandfather. She could finally convince him not to shift, since adequate safety measures to avoid any nuclear mishap have already been taken by the Government before starting nuclear thermal power plants.

(*i*) What is the value displayed by Rashi in convincing her grandfather?

(*ii*) What is the principle behind working of nuclear reactor?

(*iii*) What are the main components of nuclear reactor?

(*iv*) Why is heavy water used as moderator?

**Answer:**

(*i*) Rashi is attached to her native place.

(*ii*) A Nuclear reactor works on the principle of nuclear fission

(*iii*) Moderator, Cadmium rods

(*iv*) Heavy water (D_{2}O) is used to slow down the speed of fast moving neutrons.

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**All the questions and solutions are available in the eBook (link to access the file is given at the end)**

**Class 12th Chemistry Guess Paper:**

This solved Guess Paper has 5 sections (i.e., Section A, Section B, Section C, Section D and Section E)

- Section ‒ A contains question number 1 to 5 (very Short Answer type questions of one mark each)
- Section ‒ B contains question number 6 to 10 (Short Answer type I questions of two marks each)
- Section ‒ C contains question number 11 to 22 (Short Answer type II questions of three marks each)
- Section ‒ D contains question number 23 (value Based Question of four marks)
- Section ‒ E contains question number 24 to 26 (Long Answer type questions of five marks each)

Internal choices are present in short answer types questions and long answer type questions (Similar to latest CBSE Class 12 Chemistry Examination Pattern 2017 – 2018)

**Some sample questions from the Chemistry Guess Paper are given below:**

**Question: **NO_{2} group shows its effect only at ortho- and para- positions and not at meta- position. Explain

**Solution:**

The presence of nitro group at ortho- and para-positions withdraws the electron density from the benzene ring and thus facilitates the attack of the nucleophile on haloarene. The carbanion thus formed is stabilised through resonance. The negative charge appeared at ortho- and para- positions with respect to the halogen substituent is stabilised by –NO_{2} group while in case of meta-nitrobenzene, none of the resonating structures bear the negative charge on carbon atom bearing the –NO_{2} group. So, the presence of nitro group at meta- position does not stabilise the negative charge and no effect on reactivity is observed by the presence of –NO_{2 }group at meta position.

**Question:** Name the reagents which are used in the following conversions:

(*i*) Butan-2-one to butan-2-ol

(*ii*) Phenol to 2, 4, 6-tribromophenol

(*iii*) A primary alcohol to an aldehyde

**Solution:**

(*i*) NaBH_{4}

(*ii*) Br_{2}/H_{2}O

(*iii*) Pyridinium chlorochromate (C_{2}H_{5}NH^{+}CrO_{3}Cl^{‒})

**Question: **Define the following terms:

(*a*) Emulsion

(*b*) Tyndall Effect

(*c*) Lyophobic colloids

**Solution:**

(*a*) *Emulsion:* It is a colloidal dispersion in which both the dispersed phase and the dispersion medium are liquids.

(*b*) *Tyndall Effect:* It is defined as the scattering of light by the colloidal particles present in colloidal solution.

(*c*) *Autocatalysis:* It is reaction in which one of the product acts as a catalyst then, it is called autocatalysis.

**Question: **Give reasons for the following

(*i*) Nickel does not form low spin octahedral complexes.

(*ii*) The p-complexes are known for the transition metals only.

(*iii*) Co^{2+} is easily oxidised to Co^{3+} in the presence of a strong ligand.**Solution:**

(*i*) Nickel does not form low spin octahedral complexes because ‘Ni’ has electronic configuration 3*d*^{8} 4*s*^{2}, in which two inner *d*-orbitals are not available which are required to form *d*^{2}*sp*^{3}hybridization.

(*ii*) The p**-**complexes are known for the transition metals only because they have ‘sandwich’ structure in which the metal ion lies between two planar C_{5}H_{5} rings. The bonding involves overlap of p-electrons of the C_{5}H_{5 }rings with unfilled d-orbital of the metal. So, that all M–C bonds are identical for their stability.

(*iii*) Co^{2+} is easily oxidised to Co^{3+} in the presence of a strong ligand because in presence of strong ligand, the 3d electrons pair up leaving two orbitals empty to be involved in *d*^{2}*sp*^{3} hybridisation.

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**All the questions and solutions are available in the eBook (link to access the file is given below)**