In an examination average marks was found to be 60. marks of 80 candidates had to be changed from 95

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In an examination the average marks was found to be $60.$ The marks of $80$ candidates had to be changed from $95$ to $70$ each and the average came down to $55$ marks. The total number of candidates attended the examination were

A

$250$

B

$300$

C

$400$

D

$450$

Solution

Let the number of candidates attended the examination be $'n'.$

Total marks in the examination $=60 n$

$80$ candidates marks are changed from $95$ to $70$ and average reduced to $55$ marks.

Old average $=60 \Rightarrow$ Total $=60 n$ ….$(1)$

As per new average, total marks in the examination $=55 n$

$=60 n-80 \times(95-70)$

$=60 n-2000$

$60 n-55 n=2000$

$5 n=2000$

$n=400$

Standard 13

Quantitative Aptitude

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