The length of a wooden block is 7 m 4 cm long. Cathy cut the wooden block into 3 pieces. The length of the first piece of the wooden block is 34 cm. The length of the second piece of the wooden block is 4 m shorter than the third piece. What is the length of the third piece of wooden block?
1 m = 100 cm

Difference in the length between the second and the third piece
= 4 m
= 4 x 100
= 400 cm

Length of a wooden block
= 7 m 4 cm
= 7 x 100 + 4
= 704 cm

Length of the first piece = 34 cm
Length of the second piece = 1 u
Length of the third piece = 1 u + 400 cm

1 u + 1 u + 400 + 34 = 704
2 u + 434 = 704
2 u = 704 - 434 = 270
1 u = 270 ÷ 2 = 135 

Length of the third piece of wooden block
= 1 u + 400
= 135 + 400
= 535 cm

Answer(s): 535 cm