Subtraction Word Problems Up to 20

A subtraction word problem is a short story that describes a situation where something is taken away, lost, or compared, and asks you to find the missing amount. In these problems, every number involved is 20 or less, so once you turn the story into a number sentence, you are solving something like \( 15 - 8 = 7 \). The real skill is not the calculation itself, it is figuring out which numbers to subtract and in which order.

Word problems use certain phrases to hint that subtraction is needed. Look for words such as left, remain, fewer, less, gave away, ate, used, or how many more. For example, "left" usually means something was taken away from a group, while "how many more" usually means you are comparing two amounts. Recognizing these clues helps you decide what to subtract before you even think about the numbers.

Take-away problems: Start with a total, remove part of it, and find what remains.

Example: Sam had 15 stickers. He gave 8 to his friend. How many stickers does Sam have left?

Here, 15 is the whole group and 8 is the part removed, so \( 15 - 8 = 7 \). Sam has 7 stickers left.

Comparison problems: Compare two amounts and ask how many more or fewer one group has.

Example: Mia has 14 crayons. Jake has 6 crayons. How many more crayons does Mia have than Jake?

Even though nothing is physically taken away in the story, you still subtract the smaller amount from the larger one: \( 14 - 6 = 8 \). Mia has 8 more crayons than Jake.

Missing-part problems: You know the whole and one part, and you need to find the other part.

Example: There are 20 children at the park. 12 of them are on the playground and the rest are on the field. How many children are on the field?

The whole is 20 and the known part is 12, so \( 20 - 12 = 8 \). There are 8 children on the field.

Whichever type of problem you meet, the same steps work every time.

1. Read the story carefully and picture what is happening.

2. Identify the whole amount and the part you already know, whether that part was removed, compared, or hidden.

3. Write the number sentence, always subtracting the known part from the whole, such as \( 18 - 9 = 9 \).

4. Solve using the subtraction facts up to 20 you already know, or model it with an number line up to 20 if you need extra support.

Once you have a difference, check it by adding the answer back to the number you subtracted. If \( 15 - 8 = 7 \), then \( 7 + 8 \) should equal 15. If it does not match, reread the story to make sure you subtracted the correct numbers in the correct order. This checking habit also helps when you practice completing subtraction statements up to 20, since the missing number can sit in any position in the sentence.

Two problems can use the exact same numbers but tell very different stories. "There were 20 apples, 12 were eaten" and "20 apples were split between two baskets, one has 12" both use 20 and 12, but understanding what each story asks for is what makes you a strong problem solver, not just a fast calculator. Slow down, picture the story, then let the numbers up to 20 do the rest.

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