Similar triangles — indirect measurement
Use similar-triangle proportions (equal height-to-shadow ratios) to find a missing height or shadow length. Unlimited questions, five difficulty levels, and a full worked solution every time — free.
Try one
On a sunny afternoon, a hydro pole and a cell tower cast shadows at the same time. Because the sun hits them at the same angle, height and shadow length are proportional for both. The hydro pole is 2 m tall and casts a 6 m shadow. The tower casts an 18 m shadow. How tall is the tower?
Answer: 6
See one solved, step by step
On a sunny afternoon, a hydro pole and a lighthouse cast shadows at the same time. Because the sun hits them at the same angle, height and shadow length are proportional for both. The hydro pole is 4 m tall and casts a 7 m shadow. The lighthouse is 20 m tall. How long is its shadow?
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