Video Transcript
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.
