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JEE MAIN 2019
08-04-2019 S2
Question
The sum $\sum_{k=1}^{20} k \frac{1}{2^k}$ is equal to :
Select the correct option:
A
$2-\frac{3}{2^{17}}$
B
$1-\frac{11}{2^{20}}$
C
$2-\frac{21}{2^{20}}$
D
$2-\frac{11}{2^{19}}$
✓ Correct! Well done.
✗ Incorrect. Try again or view the solution.
Solution
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