Two friends are painting a living room. Ken can paint it in 6 hours working alone. If Barbie works alone, it will take her 8 hours. How long will it take working together? Round to the nearest tenth of an hour.
A. 3.0 hours
B. 3.4 hours
C. 4.0 hours
D. 4.6 hours

Question

Two friends are painting a living room. Ken can paint it in 6 hours working alone. If Barbie works alone, it will take her 8 hours. How long will it take working together? Round to the nearest tenth of an hour.
	A.	3.0 hours
	B.	3.4 hours
	C.	4.0 hours
	D.	4.6 hours

anonymous · Answer

The combined rate is the sum of the two rates.  In addition, the rate is the reciprocal of the time it will take to do the job, so$$\frac{1}{6}+\frac{1}{8}=\frac{1}{t}\implies t=24/7$$Approximately 3.4 hours.

anonymous · Answer

thank you

anonymous · Answer

No sweat.  Do you understand the algebra to get from the equation to the answer?

anonymous · Answer

yeah i wrote down the formula

anonymous · Answer

Common denominator of the LHS is 24; after adding, take the reciprocal of both sides.

anonymous · Answer

okay :D