Machine C takes 9 minutes to cut 90 pieces of lumbers. Machine D takes 14 minutes to cut 84 pieces of lumbers. Machine E takes 8 minutes to cut 112 pieces of lumber. 

1. Which is the faster combination, C and D or D and E? (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 C alone:
9 min → 90 pieces
1 min → 90 ÷ 9 = 10 pieces

Time taken by Machine D alone:
14 min → 84 pieces
1 min → 84 ÷ 14 = 6 pieces

Time taken by Machine E alone:
8 min → 84 pieces
1 min → 112 ÷ 8 = 14 pieces

Time taken by Machine C and Machine D together:
1 min → 10 + 6 = 16 pieces

Time taken by Machine D and Machine E together:
1 min → 6 + 14 = 20 pieces

Machine D and E are the faster combination.

(b)
Number of more pieces of lumbers that can be cut by the faster combination (Machine D and E) in 1 minute
= 20 - 16
= 4 

Answer(s): (a) D, E or E, D; (b) 4