if 10 typists can type 30 letters in 30 minutes , then how many letters will 40 typists working at the same rate complete in 1 hour ?
"no . of letters typing by 10 typists in 30 minutes = 30 no . of letters typing by 10 typists in 60 minutes = 30 * 2 = 60 no . of letters typing by 40 typists in 60 minutes = 60 / 10 * 40 = 240 answer : e"
multiply(divide(multiply(const_60.0, const_3), 10), 40)