Average of 30 numbers is 15 . average of first 18 numbers is 10 and that of next 11 numbers is 20 .

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4.Average

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The average of $30$ numbers is $15 .$ The average of the first $18$ numbers is $10$ and that of the next $11$ numbers is $20 .$ The last number is

A

$56$

B

$52$

C

$60$

D

$50$

Solution

Sum of $30$ Number $=30 \times 15=450$

Last number $=450-(18 \times 10+11 \times 20)$

$=450-(180+220)=50$

Standard 13

Quantitative Aptitude

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