Machine P takes 5 minutes to cut 90 pieces of lumbers. Machine Q takes 17 minutes to cut 102 pieces of lumbers. Machine R takes 10 minutes to cut 120 pieces of lumber. 

1. Which is the faster combination, P and Q or Q and R? (Eg A, B) 
2. In 1 minute, how many more pieces of lumbers can be cut by the faster combination compared to the other combination?

(a)
Time taken by Machine P alone:
5 min → 90 pieces
1 min → 90 ÷ 5 = 18 pieces

Time taken by Machine Q alone:
17 min → 102 pieces
1 min → 102 ÷ 17 = 6 pieces

Time taken by Machine R alone:
10 min → 102 pieces
1 min → 120 ÷ 10 = 12 pieces

Time taken by Machine P and Machine Q together:
1 min → 18 + 6 = 24 pieces

Time taken by Machine Q and Machine R together:
1 min → 6 + 12 = 18 pieces

Machine P and Q are the faster combination.

(b)
Number of more pieces of lumbers that can be cut by the faster combination (Machine P and Q) in 1 minute
= 24 - 18
= 6 

Answer(s): (a) P, Q or Q, P; (b) 6