Question

1+2+3+4+5+........+250

Answer 1

using formula   $\frac{n(n+1)}{2}$]

250 x 251 / 2 = 125  x 251 = 31375

Answer 2

1+2+3+4+5+6+7+.....................+250

Here first term , a = 1
Common difference, d = a₂ - a₁
                                 = 2 - 1
                                 =1
Last term or an = 250
Number of terms = 250

Sn = n/2 [ 2a + (n-1)d]
Sn = 125[2 + 244]
Sn = 125 × 251
Sn = 31375