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4.Average
easy
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