Question

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

• A. 3675
• B. 3575
• C. 3775
• D. 3785

Answer 1

Answer:

C. 3775

$S_n=\frac({n}{2}{a+a_n})$

$n=(a_n-a)+1$

$n=100-51+1 = 50$

$S_n=\frac{50}{2}(51+100)=3775$