31.

Among the 50 students in a class, what percentage of students like biology and chemistry?

Answer : B. 46%

32.

For any n observations of data, what is the value of (∑x) - nx ?

Answer : D. 0

33.

Simplify : 0.728x0.728-0.272x0.272 0.456

Answer : B. 1

34.

If ^{x}/_{y} = ^{3}/_{5}, then 5x + 2y is equal to 5x - 2y

Answer : B. 5

35.

A person's present age is two-fifth of the age of his mother. After 8 years, he will be one half of his mother at present?

Answer : B. 40

36.

Find the value of 1.2x1.2x1.2-0.2x0.2x0.2 1.2x1.2+1.2x0.2+0.2x0.2

37.

A bicycle marked at Rs. 1,500 is sold for Rs. 1,350. What is the percentage of discount?

Answer : D. 10

38.

Which one of the following is the smallest ratio? 7 : 3, 17 : 25, 7 : 15, 15 : 23

Answer : C. 7:15

39.

In a mixture of 60 litres, the ratio of milk and water is 2 : 1. If this ratio is to be 1 : 2, then what is the quality of water to be further added?

Answer : D. 60 l

40.

Two numbers are in the ratio 3 : 5. If 9 be subtracted from each, then they are in the ratio 12 : 23. Find the second number

Answer : D. 55