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Molly · 2023年10月08日

为什么这题用的是-3.1。而不是0.9

NO.PZ2016010802000024

问题如下:

The market demand function for four-year private universities is given by the equation

Qdpr ​=84−3.1Ppr​+0.8I+0.9Ppu​

whereQdpr is the number of applicants to private universities per year in thousands, Ppr​is the average price of private universities (in thousands of USD), I is the household monthly income (in thousands of USD), and Ppu​ is the average price of public (government-supported) universities (in thousands of USD). Assume that Ppr​ is equal to 38, I is equal to 100, and Ppu​ is equal to 18.

The price elasticity of demand for private universities is closest to:

选项:

A.

–3.1.

B.

–1.9.

C.

0.6.

解释:

B is correct.

From the demand function:

ΔQdpr/ΔPpr​=−3.1

Solve for Qdpr = 8r−3.1Ppr​+0.8I+0.9Ppu

=84−3.1(38)+0.8(100)+0.9(18)=62.4

At Ppr​ = 38, price elasticity of demand=(ΔQdpr​/ΔPpr)(Ppr​/Qdpr​)​=(-3.1)(38/62.4)=-1.9

考点:需求价格弹性

解析:题目给出了需求函数的表达式,带入数字,先求的私立大学的需求量,即:

Qdpr = 8r−3.1Ppr​+0.8I+0.9Ppu

=84−3.1(38)+0.8(100)+0.9(18)=62.4

之后我们再利用需求价格弹性公示求解,即,

(ΔQdpr​/ΔPpr)(Ppr​/Qdpr​)​=(-3.1)(38/62.4)=-1.9

为什么这题用的是-3.1。而不是0.9

1 个答案

笛子_品职助教 · 2023年10月09日

嗨,爱思考的PZer你好:


PU代表的是公立大学,题目要求的是PR,私立大学。


对应关系见下图红色画线内容:



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虽然现在很辛苦,但努力过的感觉真的很好,加油!