Bob can type two recommendation letters in 4 hours while Bill can accomplish the same task in 6 hours. How many hours would it take them, working together, to type six letters?
Mathematics · Middle School · Tue Nov 03 2020
Answered on
Given :
Bob can write 2 letters in 4 hours.
So, letter per hour written by bob = 2/4
= 1/2 letter
Bill can write 2 letters in 6 hours.
So, letter per hour written by Bill = 2/6
= 1/3 letter
Thus, production rate of bob and Bill = 1 /2 + 1 /3
= (3 + 2)/6
= 5/6
Production rate of 6 letters can be given by :
Rate × time = letters
5/6 × time = 6
time = 6 × 6/5
= 36/5
= 7 1/5 hours
Thus, it would take bob and Bill together 7 1/5 hours to write 6 letters.