题目

Water has been poured into an empty rectangular tank at the rate of 5 cubic feet per minute for 6 minutes. The length of the tank is 4 feet and the width is of the length. How deep is the water in the tank? (1 foot = 12 inches)


选项

A.

7.5 inches

B.

3 feet 7.5 inches

C.

3 feet 9 inches

D.

7 feet 6 inches

E.

30 feet

解析

如果以每分钟5立方英尺的速度向长方体水箱注水,持续6分钟, 水箱的体积将是30立方英尺。 长方体水箱的体积公式为:\( 体积 = 长×宽×高 \) 已知: 长(\( l \))= 4英尺 宽(\( b \))= \( \frac{1}{2}×长 = \frac{1}{2}×4 = 2 \)英尺 设水箱的高为\( x \),代入体积公式: \( 4×2×x = 30 \) 解得:\( x = \frac{15}{4} = 3.75 \)英尺 = 3英尺9英寸(因为1英尺=12英寸)(选项C)
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