100+ Average TNPSC Aptitude Questions and Answers - 1

Question: 1

The average marks of a student in 4 subjects is 75. If the student obtained 80 marks in the fifth subject, then the new average is

(A) 72

(B) 74

(C) 76

(D) 77

Ans: C

Sum of marks in 4 subjects = 75 × 4 = 300.

Sum of marks in 5 subjects = 300 + 80 = 380.

∴ New average = $${380}/{5}$$ = 76.

Question: 2

The average weight of a group of 75 girls was calculated as 47 kgs. it was later discovered that the weight of one of the girls was read as 45 kgs. Whereas her actual weight was 25 kgs. What is the actual average weight of the group of 75 girls? (Rounded off of two digits after decimal)

(A) 30

(B) 36

(C) 46.73

(D) 48

Ans: C

Average weight of 75 girls = 47 kgs.

Total weight of 75 girls = 47 × 75 = 3525 kg.

Actual weight of 75 girls = x

Correct weight of 75 girls

3525 - 45 + 25 = 3525 - 20 = 3505 kg

∴ Required average weight = x = $${3505}/{75}$$ = 46.73 kg.

Question: 3

Find the average of all prime numbers between 30 and 50.

(A) 37.8

(B) 39.2

(C) 39.8

(D) 39.9

Ans: C

There are five prime numbers between 30 and 50.

They are 31, 37, 41, 43 and 47.

∴ Required average = $$({31 + 37 + 41 + 43 + 47} / {5})$$ = $${199}/{5}$$ = 39.8.

Question: 4

The average age of 35 students in a class is 16 years. The average age of 21 students is 14. What is the average age of remaining 14 students?

(A) 15 years

(B) 17 years

(C) 19 years

(D) 20 years

Ans: C

Average age of 35 students = 16

Average age of 21 students = 14

∴ Average age of remaining 14 students = $${35 × 16 - 21 × 14}/{14}$$

= 5 × 8 - 21 = 40 - 21 = 19 years.

Question: 5

A student obtained the following marks in percent ages in his semester examination English 50, Maths 65, Statistics 70, Economics 63. The weights of these subjects are 2, 2, 1, 1 and 1 respectively. What is the weighted arithmetic mean?

(A) 60

(B) 61

(C) 62

(D) 63

Ans: A

Weighted arithmetic mean = $${50 × 2 + 65 × 2 + 70 × 1 + 58 × 1 + 63 × 1} / {2 + 2 + 1 + 1 + 1}$$

= $${100 + 130 + 70 + 58 + 63} / {7}$$

= $${421} / {7}$$ = 60.14 = 60.

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