Problem Solving

Someone please help me with this question:

A certain hotel has 1,400 single rooms and 420 double rooms. Each room is cleaned by one person. If one person can clean a single room every 15 minutes and a double room every 20 minutes, how many cleaning persons are needed to clean all of the rooms if each person works for exactly 7 hours?

A) 65
B) 70
C) 80
D) 90
E) 265
Thanks!

7 Hrs = 420 mins

1 Person takes 15 mins to clean the room, so in 420 mins he can clean 28 rooms.
So, 50 Person will be required to clean 1400 rooms.

1 Person takes 20 mins to clean the double room, so in 420 mins he can clean 21 double rooms.
So, 20 Person will be required to clean 420 rooms.

50 + 20 = 70

Ans B

ohinds wrote:Someone please help me with this question:

A certain hotel has 1,400 single rooms and 420 double rooms. Each room is cleaned by one person. If one person can clean a single room every 15 minutes and a double room every 20 minutes, how many cleaning persons are needed to clean all of the rooms if each person works for exactly 7 hours?

A) 65
B) 70
C) 80
D) 90
E) 265
Thanks!

each person works for 7*60 minutes, total minutes of work to be done 1400*15+420*20,

So number of people required = (1400*15+420*20)/(7*60) = 70 .. which is your answer.

Regards

Thanks for the help!