CBSE Class 10 Mathematics 2019 Previous Year Question Paper Delhi Set-3

Class X

(CBSE 2019)

Mathematics

Delhi (Set-3)

General Instructions:

(i) All questions are compulsory.

(ii) The question paper consists of 30 questions divided into four sections – A, B, C and D.

(iii) Section A comprises 6 questions of 1 mark each. Section B contains 6 questions of 2 marks

each. Section C contains 10 questions of 3 marks each. Section D contains 8 questions of 4

marks each.

(iv) There is no overall choice. However, an internal choice has been provided in two questions

of 1 mark, two questions of 2 marks, four questions of 3 marks each and three questions

of 4 marks each. You have to attempt only one of the alternative in all such questions.

(v) Use of calculators is not permitted.

Question 1

Two positive integers a and b can be written as a = x3y2 and b = xy3. x, y are prime

numbers. Find LCM (a, b).

SOLUTION:

Given: 𝑎= 𝑥3𝑦2 𝑎𝑛𝑑 𝑏= 𝑥𝑦3 where a and b are positive integers and x and y are

prime numbers.

Question 2

How many two digits numbers are divisible by 3?

SOLUTION:

The first two digit number that is divisible by 3 is 12

So, the series starts from 12

And the highest two digit number that is divisible by 3 is 99

So, the sequence becomes:

12, 15, ..., 99.

We, need to find the numbers in the given sequence

Using 𝑎𝑛= 𝑎+ (𝑛−1)𝑑

a is the first term, d is the common difference, n is the number of terms and an is the nth

term a = 12, d = 3, an= 99 substituting the values we get

Therefore, there are total 30 two digit numbers that are divisible by 3.

Question 3

In Fig. 1, DE || BC, AD = 1 cm and BD = 2 cm. What is the ratio of the ar (Δ ABC) to the

ar (Δ ADE)?

SOLUTION:

It is given that AD=1cm, BD=2 cm and DE||BC

Ratio of area of similar triangles is equal to the square of the ratio of corresponding

sides.