Multiplying fractions by whole numbers word problem | Math | 4th grade | Khan Academy

Rishi spent 34s of an hour for 2 days working on his science project. Kyle spent 1/4 of an hour for six days working on his science project. Who spent more time on his science project?

So we want to know who spent more time. To do that, we need to first know the amount of time Rishi and Kyle each spent on their science projects. So let's start with Rishi and see what we know about him.

Rishi spent 34s of an hour for two days. So, two times he spent 34s of an hour. Another way we could say this is he spent 34s of an hour once. Plus, on a second day, he spent another 34s of an hour. So, 34s plus another 34s will give us a total of 64s, or 64 hours, that Rishi spent on his science project.

Now, let's look at Kyle. Kyle spent a fourth of an hour. So, here's Kyle: he spent a fourth of an hour, but he did this for six days. So, six times, he spent a fourth of an hour. We could say that Kyle spent a fourth of an hour one day, plus a fourth of an hour a second day, a fourth of an hour a third day, a fourth day, a fifth day, and then a sixth day. He spent a fourth of an hour, so six times 1, 2, 3, 4, 5, 6. He spent a quarter, or a fourth of an hour, working on his project.

So, if we have 6 1/4s, then we have a total of 64ths. So, Kyle spent 64s, or 64 hours.

Now back to our question, now that we know how much each of them spent. Who spent more time working on his science project: Rishi with 6/4 hours or Kyle with 64 hours? The answer here, of course, is that these are equal. These are the same. Rishi and Kyle spent the same amount of time working on each of their science projects.