Video: Expressing a Given Quantity as a Unit Rate

The grocery store sells a dozen doughnuts for $5.52. How much does one doughnut cost?

02:06

Video Transcript

The grocery store sells a dozen doughnuts for five dollars 52 cents. How much does one doughnut cost?

A dozen is equal to 12. So 12 doughnuts are sold for five dollars 52 cents. We want to calculate how much one doughnut costs. We could do this by dividing five dollars and 52 cents by 12. Whilst this would be straightforward on a calculator, let’s look at an alternative method that we could use if we don’t have one.

We can begin by calculating the cost of six doughnuts. We do this by dividing the cost of 12 doughnuts by two. Dividing by two is the same as halving a number. A half of five dollars is two dollars 50. And a half of 52 cents is 26 cents. This means that six doughnuts cost two dollars and 76 cents. We can repeat this process to calculate the cost of three doughnuts. One-half of two dollars is one dollar and one-half of 76 cents is 38 cents. This means that three doughnuts cost one dollar and 38 cents.

Our final step to calculate the cost of one doughnut would be to divide this by three. This could be done using the bus stop method. 1.38 divided by three is equal to 0.46. This means that the unit cost or cost of one doughnut is 46 cents. We could check this by multiplying 46 cents by 12. This does give us a total cost of five dollars and 52 cents. So our answer is correct.

Nagwa uses cookies to ensure you get the best experience on our website. Learn more about our Privacy Policy.