Question

You are checking the intermediate results of a phone app that calculates the weight of an object in kilograms given the weight in pounds. The particular calculation you are checking, shown below, is for an input weight of 142 pounds and outputs 29.3 kilograms. What is the first step that has an error, and why is it an error?

Answer 1

The wrong step is step 4, because you only need one conversion.

The formula to convers pounds to kilograms is

$\text{weight in pounds} = 2.2 \times \text{weight in kilograms}$

Obviously, the inverse formula is

$\text{weight in kilograms} = \cfrac{\text{weight in pounds}}{2.2}$

So, you're given an input of 142 pounds. To convert it in kilograms, plug that value into out formula:

$\text{weight in kilograms} = \cfrac{142}{2.2} \approx 64.5$

and this is the answer you're looking for, so you need no more steps.