Operations & Word Problems

Depth · one concept from first principles · step 2 of 4

Change the unit using a decimal

A car travels 160 km160\ \text{km} in 11 hour 4848 minutes. If it keeps a steady speed, how many kilometers does it travel in one hour? Give the answer rounded to one decimal place.

Number systemRatios
Your answer
How to solve
Strategy Analyze the Units — The distance is per hour, so the time has to be measured in hours before anything can be divided. Minutes are sixtieths of an hour, and turning them into a decimal is the whole first half of the problem.
1STEP 1

Turn the minutes into part of an hour

There are 60 minutes in an hour, so divide the minutes by 60.

48 ÷ 60 = 0.8
2STEP 2

Divide the distance by the time

The distance in one hour is the whole distance shared over the hours taken.

160 ÷ 1.8 = 88.888…
3STEP 3

Round to one decimal place

Look at the second decimal place to decide: it is 8, so the first decimal place rounds up.

88.88… ≈ 88.9
Answer
88.9 km
Multiply back: 88.9 × 1.8 ≈ 160.0 km, matching the distance given.
Takeaway

Minutes are sixtieths of an hour -- turn them into a decimal before dividing.

  • Turn the minutes into part of an hour
  • Divide the distance by the time
  • Round to one decimal place
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