Machine Y takes 6 minutes to cut 78 pieces of lumbers. Machine Z takes 12 minutes to cut 120 pieces of lumbers. Machine A takes 8 minutes to cut 120 pieces of lumber. 

1. Which is the faster combination, Y and Z or Z and A? (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 Y alone:
6 min → 78 pieces
1 min → 78 ÷ 6 = 13 pieces

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

Time taken by Machine A alone:
8 min → 120 pieces
1 min → 120 ÷ 8 = 15 pieces

Time taken by Machine Y and Machine Z together:
1 min → 13 + 10 = 23 pieces

Time taken by Machine Z and Machine A together:
1 min → 10 + 15 = 25 pieces

Machine Z and A are the faster combination.

(b)
Number of more pieces of lumbers that can be cut by the faster combination (Machine Z and A) in 1 minute
= 25 - 23
= 2 

Answer(s): (a) Z, A or A, Z; (b) 2