what is the average of first 21 multiples of 8 ?
"required average = 8 ( 1 + 2 + . . . . + 21 ) / 21 ( 8 / 21 ) x ( ( 21 x 22 ) / 2 ) ( because sum of first 21 natural numbers ) = 88 e"
multiply(divide(divide(multiply(21, add(21, const_1)), const_2), 21), 8)