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Finding reasonable unit of measurement example

Sal chooses reasonable units of time activities like baking cookies. Created by Sal Khan.

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Video transcript

Identify the most reasonable units to measure each of the following choices. So the time it takes to bake one pan of cookies. Let's see, that's usually in the minutes, so I'll go with minutes unless you're doing some type of slow baking. But I'll say minutes is a reasonable unit here. The time it takes to pour a cup of coffee. Well, that might take you, at most, 1 or 2 seconds. So you definitely don't want to do it in hours or years. And we already used up minutes, and you definitely don't want to use minutes either. It's only a few seconds. The time it takes to drive from Chicago to Saint Louis. Well, that hopefully won't take you years. That'll take you-- I don't know the exact distance, but it's going to take you several hours to do that. So I will go with hours. Let's do a few more of these. Identify the most reasonable units to measure each of the following choices below. So we have kilometers, meters, and millimeters. And a kilometer, of course, kilo tells us that's equivalent to 1,000 meters. And milli means one-thousandth of a meter. Or another way of thinking about it, a meter is 1,000 millimeters and a kilometer is 1,000 meters. The length of a ladybug. Well, the length, unless it's some kind of monster ladybug, we're probably thinking in millimeters. The height of an average person. So an average person is multiple meters. It's going to be at least 1 meter tall and more likely closer to 2 meters. Especially your average male, adult male, would be right around 2 meters tall. So I would go with meters. The length of a marathon. So this is a long-distance race we're talking about here. If you're used to thinking in US customary units, a marathon is 26 miles. A kilometer isn't quite equal to a mile. 1.6 kilometers is equal to a mile, but it also makes sense to measure this in kilometers. You would measure the length of a marathon in miles or kilometers. You'd measure the height of an average person, if you're using US customary units, you would do it in feet. If you're using metric units, you would do it in meters. The distance between San Francisco and Los Angeles. So once again, this is several thousand kilometers. We'll go with kilometers. Or actually, San Francisco to Los Angeles is several hundred kilometers. I thought that said New York to Los Angeles. San Francisco to Los Angeles, several hundred kilometers, but still you want to do kilometers. The length of an average-sized swimming pool. Well, meters seems like a reasonable measure there. Your average pool might be 25 meters or 50 meters or something like that. The thickness of a slice of bread. So a slice of bread, it's definitely a lot thinner than a meter, so I'm going to go with the millimeters. Let me check our answer. That right. Let's do one more. Identify the most reasonable units to measure the weight of each of the following choices below. So see, we have ounces and pounds. And just as a reminder, 1 pound is equal to 16 ounces or an ounce is equal to a sixteenth of a pound. So a couch-- well, that's going to be many, many, many pounds, probably over 100 pounds. So we definitely want to put this in the pounds category. A cookie-- unless it's a really large cookie, it's going to weigh less than a pound. So I'm comfortable going-- it seems reasonable to go with ounces. A television-- well, they're getting lighter every day, but they still weigh a good bit. They still weigh multiple pounds, usually multiple tens of pounds. So we'll go with pounds. A cracker-- and once again, unless we're talking about a really huge cracker, most crackers are very, very light, lighter than even a cookie, so we will go with ounces.