mia ran 8 laps around the campus in 4 minutes. At that rate, how many laps did she run in 15 minutes?

Question

help with proportional r

Answer 1

It helps to know what the said rate is. Rate is defined as distance/time (r = d/t), in this case, distance is 8 laps and time is 4 min., so by our definition of rate, Mia was running 2 laps per minute.

Now we want to know the total distance for a given time and rate. In general we use r = d/t and multiply both sides to get

 

r*t = d

 

meaning, rate * time = distance. This makes since because if you went 80 mph for an hour, you would've gone 80 miles.

 

In Mia's case, we said r = 2 laps per min (lpm). and that t = 15 minutes, so d =  2 lpm * 15 min = 30 laps.

 

Notice, the units used are important. If the question had asked about 1/4 hr. we would've needed to convert that to 15 minutes first.

Answer 2

8/4 = l/15

 

Cross multiply.

 

4l = 120

l = 30