Question

1+2+3+4+5+6+7+8+9+10+11+12+13+14+15+16+17+18+19+20..........+100

Answer 1

a= 1

d = 1

n = 100

Sn = n/2 [2a+(n-1)d]

S100 = 50[2 + 99]

S100 = 50 × 101 = 5050

Answer 2

a=1          d=1             sn=100
therefore  ,  sn=n/2(2a +(n-1)d)
s100= 50(2*1+99*1)
            =50 *101=5050