Three planks of different lengths, C, D and E are nailed together to make a frame as shown. Plank C has 3 holes which divide it into 4 equal parts. Plank D has 4 holes which divide it into 5 equal parts and Plank E has 5 holes which divide it into 6 equal parts. In the frame, the holes U, V and W are three corners of an equilateral triangle. Plank C is 360 cm long. What is the total length of Plank C, Plank D and Plank E?
Length of Plank C = 360 cm

Length of each interval of Plank C
= 360 ÷ 4
= 90 cm

Length of 2 intervals of Plank C
= 2 x 90
= 180 cm

Length of each interval of Plank D 
= 180 ÷ 3
= 60 cm

Length of Plank D
= 5 x 60
= 300 cm

Length of each interval of Plank E
= 180 ÷ 4
= 45 cm

Length of Plank E
= 6 x 45
= 270 cm

Total length of Plank C, Plank D and Plank E
= 360 + 300 + 270
= 930 cm

Answer(s): 930 cm