The length of a plank is 7 m 5 cm long. Barbara cut the plank into 3 pieces. The length of the first piece of the plank is 63 cm. The length of the second piece of the plank is 2 m shorter than the third piece. What is the length of the third piece of plank?
1 m = 100 cm

Difference in the length between the second and the third piece
= 2 m
= 2 x 100
= 200 cm

Length of a plank
= 7 m 5 cm
= 7 x 100 + 5
= 705 cm

Length of the first piece = 63 cm
Length of the second piece = 1 u
Length of the third piece = 1 u + 200 cm

1 u + 1 u + 200 + 63 = 705
2 u + 263 = 705
2 u = 705 - 263 = 442
1 u = 442 ÷ 2 = 221 

Length of the third piece of plank
= 1 u + 200
= 221 + 200
= 421 cm

Answer(s): 421 cm