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Word problems with mass

CCSS.Math:

Video transcript

let's see if we can get a sense of different masses and we're going to do that by doing the arithmetic word problems with mass on Khan Academy so it says which is the closest to the mass of a cow so it's either seven kilograms or seven hundred 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 fifteen or sixteen 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 seven hundred kilograms that actually seems a little bit more right that's going to be closer to that's going to be closer to 1,500 pounds cows are really really big animals and they weigh a lot so I would go with seven hundred kilograms because seven kilograms is just ridiculous that's the size of a of a yeah as I've 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 video in the last exercise we saw we were talking about seven kilograms or 700 kilograms when you put a Killough in front of gram that means 1,000 grams so seven kilograms is seven thousand grams here we're just talking 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 what the mass of seven magic wands well if each of them are six grams and we have seven of them seven times 6 is 42 so we're going to have 42 42 grams let's keep going this is fun all crayons at Karen's crayon factory have the same mass Karen weighs 7 crayons and find that they have a total mass of 56 grams what is the mass of one of the crayons so 7 crayons have a mass of 56 grams so the mass of each of them well let's just take 56 and divide it by 7 by the 7 crayons well 56 divided by 7 is 8 7 times 8 is 56 so the mass of each crayon is 8 grams and you could even check that 7 crayons times 8 grams per crayon is going to be 56 grams this is surprisingly fun Tina has 5 pencils all of her pencils have the same mass Tina finds the mass of one pencil shown below and it's 8 grams what is the total mass of 5 pencils well if one pencil is 8 grams 5 pencil is going to be 5 times 8 grams well 5 times 8 is 40 it's going to be 40 40 grams all right this one seems similar although Sophia is squirrel all of Sophia's squirrels acorns have the same mass Sophia squirrel finds the total mass of our four acorn 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 4 or 4 acorns or 20 grams so what's the mass of each of them well 4 times what is 20 or 20 divided by 4 is what well 20 divided by 4 is 5 so 5 10 15 20 so if each of them are 5 grams 5 grams times 4 is going to be going to have a mass of 20 grams