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Current time:0:00Total duration:4:01

Word problems with mass

CCSS.Math:

Video transcript

- [Voiceover] Let's see if we can get a sense of different masses, and we're gonna do that by doing the arithmetic word problems with mass on Kahn Academy. So it says which is the closest to the mass of a cow? So it's either seven kilograms or 700 kilograms. So let's think about what seven kilograms would be. So one kilogram if you're used to dealing with pounds, one kilogram is 2.2 pounds. So seven kilograms is like 15 or 16 pounds. That would be the weight of maybe a large cat, or a several-month-old baby. That would be seven kilograms. So most cows are not the size of just a large cat, they are much bigger than that. 700 kilograms, that actually seems a little bit more right. That's going to be closer to 1500 pounds. Cows are really, really big animals, and they weigh a lot. So I would go with 700 kilograms, because seven kilograms is just ridiculous. That's the size of a, as I said, a large cat. Let's keep going. All of Glinda's magic wands have the same mass. Glinda knows the mass of one magic wand. What is the total mass of seven magic wands? So it tells us the mass of one magic wand is six grams. And just so you know, six grams is not a lot. So you might, in the last exercise we saw, we were talking about seven kilograms, or 700 kilograms. When you put a kilo in front of gram, that means 1000 grams. So seven kilograms is 7,000 grams. Here we're just taking about straight-up grams. So grams are not much mass at all. If you were to think about a teaspoon of sugar, that's about four or five grams of sugar. So this wand is very very light. But anyway, what they're asking us is what would be the mass of seven magic wands? Well if each of them are six grams, and we have seven of them, seven times six is 42. So we're gonna have 42 grams. Let's keep going, this is fun. All crayons at Caryn's Crayon Factory have the same mass. Caryn weighs seven crayons and finds that they have the total mass of 56 grams. What is the mass of one of the crayons? So seven crayons have a mass of 56 grams. So the mass of each of them, let's just take 56 and divide it by seven, by the seven crayons. Well 56 divided by seven is eight. Seven times eight is 56. So the mass of each crayon is eight grams. And you could even check that. Seven crayons times eight grams per crayon, is going to be 56 grams. This is surprisingly fun. Tina has five pencils. All of her pencils have the same mass. Tina finds the mass of one pencil shown below. And it's eight grams. What is the total mass of five pencils? Well if one pencil is eight grams, five pencils are gonna be five times eight grams. Well five times eight is 40. It's going to be 40 grams. All right, this one seems similar. All of Sophia's Squirrel's acorns have the same mass. Sophia's squirrel finds the total mass of her four acorns shown below. What is the mass of one of the acorns? So here, actually this is a little different than the last one, they find the mass of all four acorns are 20 grams. So what's the mass of each of them? Well, four times what is 20? Or 20 divided by four is what? 20 divided by four is five. So five, 10, 15, 20. So if each of them are five grams, five grams times four is gonna have a mass of 20 grams.