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Subtracting Ones From Teen Numbers: Number Line

In this video, we will learn how to model subtraction of a one-digit number from a teen number on a number line.

Teen numbers have two digits. A tens digit and a ones digit. The number 11 has one 10 and one one. The numbers 11, 12, 13, 14, 15, 16, 17, 18, and 19 are all teen numbers. When we subtract a one-digit number from a teen number, we can use a number line to help.

In this question, we need to subtract eight from 17, so we need to start at number 17 on our number line. And then we need to subtract eight. If we subtract seven from number 17, that will take us to 10. But we’re not subtracting seven. We have to subtract eight. As eight is one more than seven, we need to subtract one more, which takes us to number nine. So 17 subtract eight equals nine.

We subtracted eight in two steps. First, we subtracted seven, and then we subtracted one more. Seven and one is eight. So when we’re subtracting a one-digit number from a teen number on a number line, first we subtract to 10 and then we subtract the rest. Let’s try some practice questions.

What is 13 minus four? 13 minus four equals what. Hint: Finish the calculation on the number line. How many more do you have to take away?

We’re being asked to calculate 13 take away four using a number line. We’ve started to count back from 13 on the number line. We’ve counted back three spaces, and we’ve landed on number 10. We need to subtract four. We’ve already subtracted three. How many more do we need to subtract?

We know that three and one makes four, so we need to subtract one more. We landed on number nine. 13 minus four is nine. First, we subtracted three to take us to 10. Then we subtracted one more. To subtract four, first we can subtract three and then subtract one more. 13 minus four is nine.

Use the number line to subtract. 13 subtract five equals what. Hint: Subtract to make 10 first.

In this question, we have to subtract five from the number 13 and we have to subtract to 10 first. What did we have to subtract from 13 to take us to number 10? 13 take away three equals 10. We’re subtracting five. We’ve already subtracted three. How much more do we need to subtract? We know that three and two makes five, so we need to subtract two more. 10 subtract two equals eight. 13 subtract five equals eight. First, we subtracted three to make 10. Then we subtracted two more.

Help Emma answer a subtraction problem. She wants to find 13 take away seven. First, she took away three to make 10. How much is left to take away? What is 13 take away seven? 13 take away seven equals what.

We know that Emma is subtracting seven from 13. She’s already taken away three. How much more does she need to take away? We know that seven is three and four. Let’s take away four more. One, two, three, four. We landed on number six. 13 take away seven equals six. First, we subtracted three to take us to 10. Then we subtracted four more. Seven is three and four more. 13 take away seven equals six.

We’ve learned that when we subtract a one-digit number from a teen number on a number line, first we subtract 10 and then we subtract the rest.