题目

In rectangle A, the ratio of the length to the width is 3: 1. In rectangle B, the ratio of the length to the width is 4: 1. The area of rectangle A is 27 percent of the area of rectangle B. The perimeter of rectangle A is v percent of the perimeter of rectangle B.

Quantity A

v

Quantity B

54

选项

A.

Quantity A is greater.

B.

Quantity B is greater.

C.

The two quantities are equal.

D.

The relationship cannot be determined from the information given.

解析

在矩形\(A\)中,长与宽的比例为\(3:1\)。在矩形\(B\)中,长与宽的比例为\(4:1\)。矩形\(A\)的面积是矩形\(B\)面积的\(27\%\)。矩形\(A\)的周长是矩形\(B\)周长的\(v\%\)。设矩形\(A\)的宽为\(x\),则长为\(3x\),其面积\(S_{A}=3x\times x = 3x^{2}\),周长\(P_{A}=2\times(3x + x)=8x\)。 设矩形\(B\)的宽为\(y\),则长为\(4y\),其面积\(S_{B}=4y\times y=4y^{2}\),周长\(P_{B}=2\times(4y + y) = 10y\)。 已知\(S_{A}=0.27S_{B}\),即\(3x^{2}=0.27\times4y^{2}\) \[ \begin{align*} 3x^{2}&=1.08y^{2}\\ x^{2}& = 0.36y^{2}\\ x&=0.6y \end{align*} \] 将\(x = 0.6y\)代入\(P_{A}\)和\(P_{B}\)中计算\(v\)的值。 \(P_{A}=8\times0.6y = 4.8y\),\(P_{B}=10y\) 因为\(P_{A}=v\%\times P_{B}\),即\(4.8y=\frac{v}{100}\times10y\) \[ \begin{align*} 4.8y&=\frac{v}{10}y\\ v&=48 \end{align*} \] 由于\(48<54\),所以\(v < 54\),即\(Quantity\ B\)更大,答案是\(B\)
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