Machine D takes 6 minutes to cut 102 pieces of lumbers. Machine E takes 10 minutes to cut 70 pieces of lumbers. Machine F takes 11 minutes to cut 143 pieces of lumber. 

1. Which is the faster combination, D and E or E and F? (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 D alone:
6 min → 102 pieces
1 min → 102 ÷ 6 = 17 pieces

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

Time taken by Machine F alone:
11 min → 70 pieces
1 min → 143 ÷ 11 = 13 pieces

Time taken by Machine D and Machine E together:
1 min → 17 + 7 = 24 pieces

Time taken by Machine E and Machine F 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
= 24 - 20
= 4 

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