Asked by Jennifer

Edward can paint a bedroom in 3hr. Jeb can paint the same room in 3.75 hours. How long will it take them, working together, to paint the bedroom?

Answers

Answered by Ms. Sue
Their average time for painting the bedroom is 3.375 hours. Working together they'd take 3.375/2 = 1.67875 hours.
Answered by Jennifer
This is actually a multiple choice question and the choices are:
a.)20/3 hr
b.)2/13 hr
c.)5/3 hr
d.)1.5 hr

Would the answer be c?
Answered by Jennifer
How did you know to take the average of 3.75 and divide it by 2?
Answered by Reiny
I must respectfully disagree with Ms. Sue

Edwards rate = room/3
Jeb's rate = room/3.75

their combined rate = room/3 + room/3.75
= (3.75room + 3room)/(3x3.75(
= 6.75room/11.25

so Time = room/(6.75room/11.25)
= 11.25/6.75
= 1.666... hours

I know that my answer is "very close" to Ms. Sue's, but they are not the same.
Had the two times to paint the room been more diverged, the difference in the times would have been more obvious.

This question falls in the same category as the following:
Bob drives 100 miles at 50 mph, then Steve takes over and drives the next 100 miles at 80 mph.
What was the average speed for the trip.
the temptation would be to say 65 mph since they both drove the same distance, but....

time taken by Bob = 100/50 = 2 hours
time taken by Steve = 100/80 = 1.25 hours, for a total time of 3.25 hours

so average rate = 200/3.25 = 61.5 mph

Answered by Jennifer
This is actually a multiple choice question and the choices are:
a.)20/3 hr
b.)2/13 hr
c.)5/3 hr
d.)1.5 hr

Would the answer be c?
Answered by Reiny
correct
5/3 = 1.6666....
Answered by Jennifer
Thank you so much. I understand now.

Related Questions