Main content

## Topic C: Place value and rounding decimal fractions

Current time:0:00Total duration:4:32

# Rounding decimals word problems

CCSS.Math:

## Video transcript

- [Instructor] Joey used
0.432 pounds of cheese to make mac-and-cheese for dinner, and we could also call this
432/1,000 pounds of cheese to make mac-and-cheese for dinner. Round the amount of cheese to the nearest tenth. So the amount of cheese once again is 0.432 pounds and just remember the places here. This is 4/10, so that's the tenths place. This is the hundredths place, and that's an S there, so tenths, hundredths, and this right over here is thousandths, thousandths place. So we wanna round to the nearest tenth. So we're gonna round to the nearest tenth. We go one place to the right. If it's five or larger, we round up. This would become a five. If it's less than five, well, if it's less than five, which is the case here, we're gonna round down to just 4/10 even. So because three is less than five, we are going to round down, and we're going to get 0.400, or we could write that as 0.4, or we could write that as 4/10 of a pound. Let's do another one. Eliza's pet snail traveled
2.197 meters in one day. Round the distance to
the nearest hundredth. So pause this video and
see if you can do that. Round the distance to
the nearest hundredth. So it's 2.197. This is the hundredths
place right over here, and so if we're gonna round
to the nearest hundredth, we're gonna go one place to the right. If this one place to the right is five or greater, we're gonna round up, and seven is five or greater, so we are going to round up . Now this is interesting 'cause if you round a nine up, you get to 10, but you can't put a
whole 10 right over here. So one way to think about it is you have a 19 here, and so if you round up, you're gonna go to a 20, or another way to think about it. If you round the nine up, you're gonna go to the next tenth. So this is going to be 2 point, you could view this as 19/100 or 19/100 and 7/1,000, and so now we're gonna round up to 20/100, so 2.20. We're rounding to the nearest hundredth, which you could write as 2.2, but to make it clear that you're rounding to
the nearest hundredth, you're gonna write 2.20, and later in your life, this actually might matter to actually show what you're rounding to. Let's do another example here. Cassandra spends 6.75
hours each day at school. Round the amount of time
to the nearest hour. Alright, so 6.75, so you might be a little confused, and actually, I encourage
you to pause the video again and try to solve it on your own. So you might be a little confused 'cause they're not saying
round it to the nearest tenth or hundredth or one or 10 or 100. They're saying to the nearest hour, but in this case, the hour is the ones place. So if we're gonna round
to the nearest hour, this is another way of saying round to the nearest one. So we're gonna round to the nearest one. We go one place to the right. We go to look at the tenths place. If it's five or larger, we round up. Well, seven is five or larger, so we round up to the next hour, which is going to be seven, so seven hours. If this was 6.49999, once again, if we're
rounding to the nearest hour, we go one place to the right. It doesn't matter that we
have all these nines here. We'd say, hey, look,
four is less than five. Therefore, we should round down, round down, and you would round down to the next hour. Well, the next hour that's below 6.499999, nine, nine, nine, nine, is six hours, but in this case, we had a
seven in the tenths place, which is definitely greater
than or equal to five, and so we'd round up to the next hour, which is seven hours.