a work crew of 6 men takes 9 days to complete one - half of a job . if 12 men are then added to the crew and the men continue to work at the same rate , how many days will it take the enlarged crew to do the rest of the job ?
"suppose 1 man can do work in x days . . so 6 men will do in . . 6 / x = 1 / 9 * 1 / 2 as half job is done x = 108 now 12 more are added then 18 / 108 = 1 / 2 * 1 / d for remaining half job d = 3 number of days b"
add(9, divide(multiply(6, 9), add(6, 12)))