Question

(51 + 52 + 53 + .........+100) is equal to

Answer 1

Step-by-step explanation:

we know that

Sn=n/2(a+l)

in above question the no of is 50

=>n=50 and a=51 , l=100

Sn=50/2(51+100)

=>25(151)= 3775

Answer 2

Answer: well another trick is there as questions is given

51+52+....+100 so answer will be :

(1+2+3+......+100)-(51+52+....+100)=3775

{Used the formula that (1+2+....n=n(n+1)/2)}

So from 1+2+...100=100(100+1)/2=10100/2...............(1)

-1+2+...+50=50(50+1)/2=2550/2..................(2)

Now substract 1&2 we get

10100/2-2550/2=7550/2=3775

Step-by-step explanation: