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​75013+750115+750135+…750199=?750 \frac13+750 \frac1{15}+750 \frac1{35}+…750 \frac1{99}=?75031​+750151​+750351​+…750991​=?​​
Question

75013+750115+750135+750199=?750 \frac13+750 \frac1{15}+750 \frac1{35}+…750 \frac1{99}=?​​

A.

37505113750\frac{ 5}{11}​​

B.

3750493750 \frac49​​

C.

37506113750 \frac6{11}​​

D.

37515113751 \frac5{11}​​

Correct option is A

Given:
The series is 75013+750115+750135+...+750199 750\frac{1}{3} + 750\frac{1}{15} + 750\frac{1}{35} + ... + 750\frac{1}{99}​​
Formula Used:
Decomposition of mixed fractions: abc=a+bca\frac{b}{c} = a + \frac{b}{c}​​
Telescoping series sum for terms of type 1n(n+2)=12(1n1n+2)\frac{1}{n(n+2)} = \frac{1}{2}(\frac{1}{n} - \frac{1}{n+2})​​
Solution:
750(1+13+1+115+1+135+1+163+1+199)750 \left(1 +\frac{1}{3} +1+ \frac{1}{15} +1+ \frac{1}{35} +1+\frac{1}{63} +1+ \frac{1}{99}\right)​​

=750(5+11×3+13×5+15×7++19×11)= 750 \left(5+\frac{1}{1 \times 3} + \frac{1}{3 \times 5} + \frac{1}{5 \times 7} + \ldots + \frac{1}{9 \times 11}\right)

=750[5+12(113)+12(1315)+12(1517)++12(19111)]= 750 \left[5+\frac{1}{2}\left(1 - \frac{1}{3}\right) + \frac{1}{2}\left(\frac{1}{3} - \frac{1}{5}\right) + \frac{1}{2}\left(\frac{1}{5} - \frac{1}{7}\right) + \ldots + \frac{1}{2}\left(\frac{1}{9} - \frac{1}{11}\right)\right]

=750×[5+12(1111)]= 750 \times \left[5+ \frac{1}{2}\left(1 - \frac{1}{11}\right) \right]​​

=750×(5+12×1011)= 750 \times\left(5+ \frac{1}{2} \times \frac{10}{11}\right)​​

=750(5+511)= 750 \left(5+ \frac{5}{11}\right)  

=3750511=3750\frac{5}{11}​​
Final Answer
So the correct answer is (a)

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