calculate the sum of first 39 natural numbers .
"solution we know that ( 1 + 2 + 3 + . . . . . + 39 ) = n ( n + 1 ) / 2 therefore ( 1 + 2 + 3 + . . . . + 39 ) = ( 39 × 40 / 2 ) = 780 . answer a"
multiply(add(39, const_1), divide(39, const_2))