the average height of 20 girls out of a class of 50 is 142 cm . and that of the remaining girls is 149 cm . the average height of the whole class is :
"explanation : average height of the whole class = ( 20 × 142 + 30 × 149 / 50 ) = 146.2 cms answer a"
divide(add(multiply(142, 20), multiply(149, const_10)), 50)