The average of a collection of 20 measurements was calculated to tb 56 cm. But later it was found that a mistake had occurred in one of the measurement which was recorded as 64 cm., but should have been 61 cm. The correct average must be -

A. 53 cm

B. 54.5 cm

C. 55.85 cm

D. 56.15 cm

Answer: Option C

Solution(By Examveda Team)

According to the question,
Correct average
= $$\frac{20 × 56 - 64 + 61}{20}$$  
= $$\frac{1120 - 3}{20}$$  
= $$\frac{1117}{20}$$  
= 55.85 cm