The sum of all even numbers between 21 and 51 is [SSC (10+2) 2010] |
A) 518
B) 560
C) 540
D) 546
Correct Answer: C
Solution :
Required sum \[=22+24+26+...+50\] |
Number of terms =15 terms |
\[{{S}_{n}}=\frac{n}{2}[2a+(n-1)d]\] |
\[=\frac{15}{2}[2\times 22+(14)\times 2]\] |
\[=\frac{15}{2}[44\times 28]=\frac{15}{2}\times 72=540\] |
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