Machine R takes 7 minutes to cut 140 pieces of lumbers. Machine S takes 16 minutes to cut 144 pieces of lumbers. Machine T takes 10 minutes to cut 100 pieces of lumber. 

1. Which is the faster combination, R and S or S and T? (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 R alone:
7 min → 140 pieces
1 min → 140 ÷ 7 = 20 pieces

Time taken by Machine S alone:
16 min → 144 pieces
1 min → 144 ÷ 16 = 9 pieces

Time taken by Machine T alone:
10 min → 144 pieces
1 min → 100 ÷ 10 = 10 pieces

Time taken by Machine R and Machine S together:
1 min → 20 + 9 = 29 pieces

Time taken by Machine S and Machine T together:
1 min → 9 + 10 = 19 pieces

Machine R and S are the faster combination.

(b)
Number of more pieces of lumbers that can be cut by the faster combination (Machine R and S) in 1 minute
= 29 - 19
= 10 

Answer(s): (a) R, S or S, R; (b) 10