32.7k views
2 votes
It takes Brian 15 hours longer to build a model car than it takes John. If they work together, they can build the model car in 4 hours. Using complete sentences, explain each step in figuring out how to determine the time it would take Brian to build the car on his own. (10 points)

User Madden
by
7.6k points

1 Answer

3 votes

Answer:

1/x + 1/( x+15 ) = 1/4 / · x ( x+15 )

x+15 + x = x ( x+15 ) /4 / · 4

8 x + 60 = x² + 15 x

x² + 15 x - 8 x - 60 = 0

x² + 7 x - 60 = 0

x² + 12 x - 5 x - 60 = 0

x · ( x + 12 ) - 5 ·( x+ 12 ) = 0

( x + 12 ) · ( x - 5 ) =0

x = - 12 ( not accepted ) or x = 5

The time taken by Brian: 5 + 15 = 20 hours

Explanation:

User Tarzan
by
8.2k points

No related questions found

Welcome to QAmmunity.org, where you can ask questions and receive answers from other members of our community.

9.4m questions

12.2m answers

Categories