Virginia SOL Math / Grade 1 / Computation & Estimation

1.CE.1

Add & Subtract Within 20

What you'll learn

  • Recall addition and subtraction facts within 10
  • Add and subtract within 20 using strategies
  • Solve single-step story problems within 20

Words to know

Add —
put groups together to find how many in all
Subtract —
take away to find how many are left
Sum —
the answer when you add
Difference —
the answer when you subtract
Fact family —
related addition and subtraction facts

Why it matters Adding and subtracting lets you find totals, know how many are left, and figure out how many more you need.

Worked examples

Model ItI do

Find 8 + 5 by making a ten.

Take 2 from the 5 to make 8 into 10. Now you have 10 + 3 left. So 8 + 5 = 13.

Try It TogetherWe do

Find 14 - 6.

Start at 14 and count back 6: 13, 12, 11, 10, 9, 8. You land on 8, so 14 - 6 = 8.

Now YouYou do

There were 9 birds. Then 4 more came. How many birds in all?

Decide whether to add or subtract, then solve. Check your answer in the back of this chapter.

Practice

Mastered 0 of 11

Warm-up

Ease in with the basics.

  1. 1.Find 3 + 4.

  2. 2.Find 6 - 2.

  3. 3.Find 5 + 5.

On Level

The core Quick Check from the book.

  1. 1.Find 7 + 6.

  2. 2.Find 15 - 8.

  3. 3.Find 9 + 9.

  4. 4.You have 12 grapes and eat 5. How many are left?

  5. 5.Write the missing number: 6 + ___ = 14.

Challenge

Stretch your thinking.

  1. 1.There were 16 apples. You gave away 9. How many are left?

  2. 2.Write the missing number: 8 + ___ = 17.

  3. 3.Find 7 + 8 by making a ten.