Chapter 4 - Proportions, Percents, and Solving Inequalities - 4.2 - Percents and Problem Solving - Problem Set 4.2 - Page 155: 28

The number we are looking for is 500.

Let X represent the number we are looking for. 2.1% of what number means 2.1% $\times$ X Is 10.5 means =10.5 So, this question translates to: 2.1% $\times$ X = 10.5 0.021 $\times$ X = 10.5 Divide both sides by 0.021 X = 500