the average height of 20 students is 20 cm and the average height of 11 students is 20 cm . what is the average height of the 31 students ?
the total height of the 31 students = ( 20 * 20 ) + ( 11 * 20 ) = 400 + 220 = 620 cm the required average height = 620 / 31 = 20 cm answer : b
divide(add(multiply(20, 20), multiply(11, 20)), 31)