Step by step
The question
Question: 3/5 kilometer in 1/4 hour: how much is that per hour?
A unit rate says how much for 1 hour.
Per hour means: divide by the hours.
1 Write the rate
Kilometers divided by hours: 3/5 ÷ 1/4.
Careful!
Not the other way round.
That would be hours per kilometer.
2 Divide
Dividing by a fraction is the same as times its flip.
Keep the first number.
Change divide to times.
Turn the second fraction upside down.
So 1/4 becomes 4, and divide becomes times.
To multiply fractions, we do top times top, and bottom times bottom.
A whole number is a fraction over 1.
3 times 4 is 12.
5 times 1 is 5.
So the unit rate is 12/5 kilometers per hour.
3 Check
Let's check: 12/5 kilometers per hour, for 1/4 hour.
12/5 times 1/4 is 3/5.
That is the kilometers we started with.
So the answer is right!
Let's look back.
First: write the rate.
Then: divide.
Last: check.