Once you attempt the question then PrepInsta explanation will be displayed.
The number series 1, 2, 3, 4, . . . . , 35, 36.
The first term a = 1
The common difference d = 1
Total number of terms n = 36
apply the input parameter values in the formula
Sum = n/2 x (a + Tn)
= 36/2 x (1 + 36)
= 1332/2
1 + 2 + 3 + 4 + . . . . + 35 + 36 = 666