Average of a collection of 20 measurements was calculated to be 56, cm . But later, it was found tha

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4.Average

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

A

$53$

B

$54.5$

C

$55.85$

D

$56.15$

Solution

Given average of $20$ measurements $=56 cm$

Sum $=56 \times 20=1120 cm$

correct average $=\frac{1120+61-64}{20}=\frac{1117}{20}=55.85 cm$

Standard 13

Quantitative Aptitude

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