Rahim averaged 70 in his first m number of exams. After taking n more exams, he had an overall average of In terms of m and n, his average for the last n exams was?

A (5m+75)/n

B (5m/n)+75

C (5n/m)+75

D (70m+75n)/(m+n)

Correct Answer: Option B

m টি exam এ মোট marks= 70m

m+n টি exam এ মোট marks= 75 (m+n)

n টি exam এর মোট marks = 75 (m+n) - 70m = 5m+75n

n টি exam এর average = (5m+75n)/n = (5m/n)+75