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    What is the value of 21×3+23×5+25×7+⋯+245×47\frac{2}{1 \times 3} + \frac{2}{3 \times 5} + \frac{2}{5 \times 7} + \dots + \frac{2}{45 \times 47}1×
    Question

    What is the value of 21×3+23×5+25×7++245×47\frac{2}{1 \times 3} + \frac{2}{3 \times 5} + \frac{2}{5 \times 7} + \dots + \frac{2}{45 \times 47} ?​

    A.

    46/47

    B.

    47/48

    C.

    49/50

    D.

    45/46

    Correct option is A

    Solution:

    21×3+23×5+25×7++245×47\frac{2}{1 \times 3} + \frac{2}{3 \times 5} + \frac{2}{5 \times 7} + \dots + \frac{2}{45 \times 47} 

    2n×(n+2)=22(1n1n+2)\frac{2}{n \times (n+2)} = \frac{2}{2} \left( \frac{1}{n} - \frac{1}{n+2} \right) 

    (1113)+(1315)++(145147)\left( \frac{1}{1} - \frac{1}{3} \right) + \left( \frac{1}{3} - \frac{1}{5} \right) + \dots + \left( \frac{1}{45} - \frac{1}{47} \right) 

    1147=46471 - \frac{1}{47} = \frac{46}{47}

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