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

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

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

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

Length of Plank G
= 5 x 20
= 100 cm

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

Length of Plank H
= 6 x 15
= 90 cm

Total length of Plank F, Plank G and Plank H
= 120 + 100 + 90
= 310 cm

Answer(s): 310 cm