Answer:
He determined pounds per dollar by dividing 10 by 25 but wrote the unit rate as a dollar value.
Explanation:
Given
![(10\ pounds)/(\$25) = (10\ pounds)/(25) / (\$25)/(25) = (0.4)/(1)](https://img.qammunity.org/2022/formulas/mathematics/high-school/vnyac9swryaznpgaef97bfxumwy35vtj9k.png)
![Unit\ Price = 40\ cents](https://img.qammunity.org/2022/formulas/mathematics/high-school/a2dwlpv06xw0q1dm2keu5xvwjehlad6q2r.png)
![40\ cents * 6 = \$2.40](https://img.qammunity.org/2022/formulas/mathematics/high-school/anwuyqb9ls5nkpdfg60l1z8zmb9xv9p17p.png)
Required
Determine Ming's error
Ming's error is from here
![(10\ pounds)/(\$25) = (10\ pounds)/(25) / (\$25)/(25) = (0.4)/(1)](https://img.qammunity.org/2022/formulas/mathematics/high-school/vnyac9swryaznpgaef97bfxumwy35vtj9k.png)
He calculated the unit rate as pound per dollar.
So, after calculating the unit rate, the unit should be:
![Unit\ Rate = 0.4\ pound/\$](https://img.qammunity.org/2022/formulas/mathematics/high-school/4bbu3g077xhop761qh8o8xmq5kbwdwndni.png)
But instead, he solved as:
![Unit\ Rate = \$0.4/ pound](https://img.qammunity.org/2022/formulas/mathematics/high-school/3b5pa74hvz5qu2oeo7l4d8kqma1jv04vua.png)
Hence, (a) is correct