Skills Handbook - Ratios and Proportions - Exercises - Page 974: 16

$541.67, 541$ if we are rounding down to the number of heart beats that were completed

Let's put this in proportion form: 130:12 = x:50 Now, let's put it in fraction form: $\frac{130}{12} = \frac{x}{50}$ Cross-multiply: $130*50 = 12*x, x = \frac{130*50}{12} = 541.67$