一条有关RATE的数学题,

题目

一条有关RATE的数学题,
(a) Bob,by himself,can paint four rooms in 10 hours.If he hires Peter to help,they can do the same job together in 6 hours.If he lets Peter work alone,how long will it take for Peter to paint the four rooms?
(b) In part(a),if Bob works alone for 4 hours,and then they work together to complete the remaining job,then how long will it take them to finish the remaining job?

答案

(a):it will take 15 hour for peter to paint the four room.
(b):it will take 3.6 hour for them to finish the ramaining job.