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Find the value of​12×4+14×6+16×8+.......+148×50:\frac{1}{2×4}+\frac{1}{4×6}+\frac{1}{6×8}+.......+\frac{1}{48×50}:2×41​+4×61​+6×81​+.......+48×501​:​​
Question

Find the value of

12×4+14×6+16×8+.......+148×50:\frac{1}{2×4}+\frac{1}{4×6}+\frac{1}{6×8}+.......+\frac{1}{48×50}:​​

A.

0.48

B.

0.42

C.

0.46

D.

0.24

Correct option is D

Given:

12×4+14×6+16×8++148×50\frac{1}{2 \times 4} + \frac{1}{4 \times 6} + \frac{1}{6 \times 8} + \cdots + \frac{1}{48 \times 50}​​

Concept Used:

1n(n+2)=12(1n1n+2)\frac{1}{n(n+2)} = \frac{1}{2} \left( \frac{1}{n} - \frac{1}{n+2} \right)

Solution:

12(1214)+12(1416)++(148150)\frac{1}{2} \left( \frac{1}{2} - \frac{1}{4} \right)+ \frac{1}{2} \left( \frac{1}{4} - \frac{1}{6} \right)+ \cdots + \left( \frac{1}{48} - \frac{1}{50} \right) ​​

=12(1214+1416+1618++148150)=\frac{1}{2} \left( \frac{1}{2} - \frac{1}{4} + \frac{1}{4} - \frac{1}{6} + \frac{1}{6} - \frac{1}{8} + \cdots + \frac{1}{48} - \frac{1}{50} \right)​​

=12(12150)=12×48100=24100=625=\frac{1}{2} \left( \frac{1}{2} - \frac{1}{50} \right) = \frac{1}{2} \times \frac{48}{100} = \frac{24}{100} = \frac{6}{25} = 0.24

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