The length of a plank is 3 m 2 cm long. Irene cut the plank into 3 pieces. The length of the first piece of the plank is 62 cm. The length of the second piece of the plank is 1 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
= 1 m
= 1 x 100
= 100 cm

Length of a plank
= 3 m 2 cm
= 3 x 100 + 2
= 302 cm

Length of the first piece = 62 cm
Length of the second piece = 1 u
Length of the third piece = 1 u + 100 cm

1 u + 1 u + 100 + 62 = 302
2 u + 162 = 302
2 u = 302 - 162 = 140
1 u = 140 ÷ 2 = 70 

Length of the third piece of plank
= 1 u + 100
= 70 + 100
= 170 cm

Answer(s): 170 cm