The length of a plank is 9 m 5 cm long. Linda cut the plank into 3 pieces. The length of the first piece of the plank is 47 cm. The length of the second piece of the plank is 3 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
= 3 m
= 3 x 100
= 300 cm

Length of a plank
= 9 m 5 cm
= 9 x 100 + 5
= 905 cm

Length of the first piece = 47 cm
Length of the second piece = 1 u
Length of the third piece = 1 u + 300 cm

1 u + 1 u + 300 + 47 = 905
2 u + 347 = 905
2 u = 905 - 347 = 558
1 u = 558 ÷ 2 = 279 

Length of the third piece of plank
= 1 u + 300
= 279 + 300
= 579 cm

Answer(s): 579 cm