Word problem ratio

Question

Jamal can type a 20 page document in 40 minute, Susan can type it in 30 minutes, & Jack can type it in 24 minutes. All working simultaneously how much time will it take them to type the same document collectively?

Answer 1

Hi, Gary,

Both of my brothers and their families live in St. Charles-their last name is Walsh. 

Anyway, the formula for working together is

time together + time together = 1

   time alone         time alone

t/40 + t/30 + t/24 = 1  Multiply both sides by the LCD, which is 120.

3t + 4t + 5t = 120

12t = 120    t = 10 minutes

Answer 2

Consider the 20 page document one job.

m represents the minutes spent typing

m/40 + m/30 + m/24 = 1

 

Can you solve for m and answer?