Video: Using Repeated Subtraction on Number Lines to Divide by 5

Mason has 20 oranges. He is going to put them into bags of 5. After he makes 2 bags of oranges, there are ＿ oranges left. When there are no oranges left, he has made ＿ bags of 5.

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Video Transcript

Mason has 20 oranges. He is going to put them into bags of five. After he makes two bags of oranges, there are what oranges left. When there are no oranges left, he has made what bags of five.

We’re told that Mason has 20 oranges. We’re also told he’s going to put them into bags of five. Mason is dividing his 20 oranges into groups of five. We can see from the number line that Mason has already made two bags of oranges. If he starts with 20 oranges and takes away one bag, which is five oranges, he will have 15 left. If he makes another bag of five, then he will have 10 oranges left.

We know that two groups of five is 10. And if Mason had 20 oranges and put 10 into bags, he would have 10 left. So the first answer is 10. After he makes two bags of oranges, there are 10 oranges left. Mason can take away another five oranges and put them into a bag. Then, he’ll have five left. Then, if he puts the remaining five oranges into a bag, there’ll be no oranges left.

The final part of the question asks us, when there are no oranges left, how many bags of five has Mason made? In other words, the question is asking us how many bags of five Mason could make from his 20 oranges. Or what is 20 divided by five. How many bags of five oranges did Mason make? If we look closely at the number line, we can see that Mason made four bags of five. We counted back in fives four times. There are four bags of five in 20 oranges. Five lots of four are 20.

If Mason has 20 oranges and he puts them into bags of five, after he makes two bags of oranges, there are 10 oranges left. And when there are no oranges left, he has made four bags of five.