A pole 18 m high stands on level ground. When the sun's altitude falls from 45° to 30°, the length of its shadow increases by:

The two shadows are 18·cot45° = 18 m and 18·cot30° = 18√3 ≈ 31.18 m, so the increase is 18√3 − 18 = 18(√3 − 1) ≈ 13.18 m. The figure 18√3 is the longer shadow itself rather than the growth, adding instead of subtracting gives 18(√3 + 1), and halving the height answers no part of the question.