Three planks of different lengths, W, X and Y are nailed together to make a frame as shown. Plank W has 3 holes which divide it into 4 equal parts. Plank X has 4 holes which divide it into 5 equal parts and Plank Y has 5 holes which divide it into 6 equal parts. In the frame, the holes C, D and E are three corners of an equilateral triangle. Plank W is 120 cm long. What is the total length of Plank W, Plank X and Plank Y?
Length of Plank W = 120 cm

Length of each interval of Plank W
= 120 ÷ 4
= 30 cm

Length of 2 intervals of Plank W
= 2 x 30
= 60 cm

Length of each interval of Plank X 
= 60 ÷ 3
= 20 cm

Length of Plank X
= 5 x 20
= 100 cm

Length of each interval of Plank Y
= 60 ÷ 4
= 15 cm

Length of Plank Y
= 6 x 15
= 90 cm

Total length of Plank W, Plank X and Plank Y
= 120 + 100 + 90
= 310 cm

Answer(s): 310 cm