Question

Shawn and Ellie are construction workers. Shawn can complete a concrete job in 4 hours, while Ellie can complete it in 6 hours. The foreman says that it will take them 5 hours to complete it if they work together. Explain each step in solving this equation, and determine if the foreman is correct or not.

Answer 1

The foreman is incorrect. If one person can finish the job alone in 4 hours then working together the job must be done faster than that

To do the proper calculation let x be the number of hours

Shawn does 1/4 of the job per hour so his contribution is

(1/4)x

Same reasoning for Ellie’s being (1/6)x

Adding them together to complete 1 full job

(1/4)x + (1/6)x = 1
Solve for x