IXL | Add and subtract integers: word problems

Read this word problem.

On a cold February morning, Colton checked the temperature on his phone and saw that it was

–

When he checked again after school, the temperature had dropped

What was the temperature after school?

To solve the problem, Ellen subtracted

–

(

–

)

and came up with an answer of

Is Ellen correct? Why or why not?

Yes, Ellen is correct.

No. Ellen should have added

–

+ 3 because she needed to add the starting temperature and the change in temperature.

No. Ellen should have subtracted

–

because the temperature started at

–

and dropped

ref_doc_title.

Learn with an example

question

Read this word problem.

When Emmett began his science experiment, he had 20 milliliters of an unknown solution. During the experiment, the change in the volume of the solution was

–

milliliters. What was the final volume of the solution?

To solve the problem, Dakota added

(

–

)

and came up with an answer of

–

milliliters. Is Dakota correct? Why or why not?

Yes, Dakota is correct.

No. The answer should have been 11 milliliters, not

–

milliliters, because the volume should not be negative.

No. Dakota should have subtracted

–

(

–

)

because the volume decreased.

key idea

To add two numbers with the same

sign,

add the absolute values of the numbers. Keep their sign. For example,

–

(

–

)

–

To add two numbers with different

signs,

subtract the absolute values of the numbers. Keep the sign of the number with the larger absolute value. For example,

–

Subtracting a number is the same as adding its opposite. For example,

–

(

–

)

–

solution

To see if Dakota is correct, start by listing the information she was given in the problem.

The volume of the solution was 20 milliliters.
The change in the volume of the solution was
–
9
milliliters.

Now write an expression that represents the situation. You need to find the final volume of the solution, so Dakota was right to add.

20	+	( – 9 )	=	?

initial volume		change in volume		final volume

Add.

(

–

)

So, the final volume of the solution was 11 milliliters. Notice that the answer is positive because the absolute value of 20 is larger than the absolute value of

–

Dakota is incorrect. The answer should have been 11 milliliters, not

–

milliliters, because the volume should not be negative.

Looking for more? Try these:

Lesson: Adding and subtracting integers

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Not feeling ready yet? These can help:

B.12Add and subtract integers

A.1Understanding integers

Lesson: Adding and subtracting integers

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