Numbers - Arithmetic Aptitude Questions and Answers

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(51 + 52 + 53 + ... + 100) = ?

2525

2975

3225

3775

Answer : Option D

Explanation :

S_n = (1 + 2 + 3 + ... + 50 + 51 + 52 + ... + 100) - (1 + 2 + 3 + ... + 50)

= $\frac { 100 } { 2 }$ x (1 + 100)- $\frac {50 } { 2 }*$ (1 + 50)

= (50 x 101) - (25 x 51)

= (5050 - 1275)

= 3775.

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