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4.Average
hard
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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