A) 200
B) 280
C) 120
D) 150
Correct Answer: A
Solution :
\[{{a}_{1}}+{{a}_{7}}+{{a}_{16}}=40\] \[a+a+6d+a+15d=40\] \[\Rightarrow 3a+21d=40\]\[\Rightarrow \] \[{{S}_{15}}=\frac{15}{2}\left( 2a+14d \right)=15\left( a+7d \right)\] \[{{S}_{15}}=15\times \frac{40}{3}\Rightarrow 200\,\,\,\,\,\,\,\,\]You need to login to perform this action.
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