Machine C takes 6 minutes to cut 66 pieces of lumbers. Machine D takes 10 minutes to cut 70 pieces of lumbers. Machine E takes 12 minutes to cut 156 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:
6 min → 66 pieces
1 min → 66 ÷ 6 = 11 pieces

Time taken by Machine D alone:
10 min → 70 pieces
1 min → 70 ÷ 10 = 7 pieces

Time taken by Machine E alone:
12 min → 70 pieces
1 min → 156 ÷ 12 = 13 pieces

Time taken by Machine C and Machine D together:
1 min → 11 + 7 = 18 pieces

Time taken by Machine D and Machine E together:
1 min → 7 + 13 = 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 - 18
= 2 

Answer(s): (a) D, E or E, D; (b) 2