model 5 find new average from error Section-Wise Topic Notes With Detailed Explanation And Example Questions

Question : 1

The average weight of 15 students in a class increases by 1.5kg when one of the students weighing 40 kg is replaced by a new student. What is the weight (in kg) of the new student ?

a) 56 kg.

b) 64.5 kg.

c) 62.5 kg.

d) 60 kg.

Question : 2

The average weight of three men A, B and C is 84 kg. D joins them and the average weight of the four becomes 80 kg. If E whose weight is 3 kg more than that of D, replaces A, the average weight of B, C, D and E becomes 79 kg. The weight of A is

a) 70 kg.

b) 65 kg.

c) 80 kg.

d) 75 kg.

Question : 3

A student finds the average of ten 2-digit numbers. While copying numbers, by mistake, he writes one number with its digits interchanged. As a result his answer is 1.8 less than the correct answer. The difference of the digits of the number, in which he made mistake, is

a) 3

b) 2

c) 6

d) 4

Question : 4

The average marks of 100 students were found to be 40. Later on it was discovered that a score of 53 was misread as 83. Find the correct average corresponding to the correct score.

a) 39

b) 38.7

c) 41

d) 39.7

Question : 5

The average marks obtained by 22 candidates in an examination are 45. The average marks of the first 10 candidates are 55 and those of the last eleven are 40. The number of marks obtained by the eleventh candidate is

a) 0

b) 45

c) 47.5

d) 50

Question : 6

In an examination, the average of marks was found to be 50. For deducting marks for computational errors, the marks of 100 candidates had to be changed from 90 to 60 each and so the average of marks came down to 45. The total number of candidates, who appeared at the examination, was

a) 300

b) 600

c) 150

d) 200