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Problem 18 - Entrance Test

A triangle has base 10 cm and height decreasing at 2 cm/min. How fast is the area decreasing when h = 6 cm (in cm²/min)?

Correct: B

A = (1/2)bh → dA/dt = (1/2)b dh/dt = (1/2)(10)(–2) = –10 cm²/min → decreasing at 10 cm²/min.