Addition and Subtraction Fluency Within 20: practice solutions, Grade 2 – download the PDF

1 Doubles ★★★

1. \(6+6=12\)
2. \(9+9=18\)
3. \(7+7=14\)
4. \(10+10=20\)

Each double is an even number.

2 Make ten ★★★

1. \(8+2=10\)
2. \(7+3=10\)
3. \(6+4=10\)

For \(9+4\): take 1 from 4 to make \(9+1=10\). Then \(10+3=13\). So \(9+4=13\).

3 Related facts ★★★

Start with the whole, 13. Subtract each part: \(13-6=7\) and \(13-7=6\).

4 Even or odd? ★★★

Even: 12, 18, and 20 (they end in 2, 8, and 0). Odd: 15, 7, and 13 (they end in 5, 7, and 3).

5 Missing addends ★★★

1. \(11-6=5\), so \(6+5=11\).
2. \(15-8=7\), so \(8+7=15\).
3. \(17-9=8\), so \(8+9=17\).

The number line shows the jump from 9 up to 17, which is 8.

6 Three numbers ★★★

\(4+6=10\). Then \(10+3=13\). So \(4+3+6=13\).

7 Sticker book ★★★

Add the parts: \(7+8\). Near double: \(7+7=14\), so \(7+8=15\).

Maya has 15 stickers.

8 Near doubles ★★★

\(6+6=12\), and 7 is 1 more than 6, so \(6+7=12+1=13\).

9 Fact family ★★★

The whole is 14. The four facts are \(5+9=14\), \(9+5=14\), \(14-5=9\), and \(14-9=5\).

10 True or false? ★★★

1. True. 8 plus 8 is a double and equals 16.
2. False. \(7+7=14\), so \(7+8=15\).
3. False. \(7+6=13\), so \(13-6=7\).
4. True. You can add in any order, so both sides equal 14.

11 Muffin tray ★★★

Solve \(18-9\). Since \(9+9=18\), we get \(18-9=9\).

There are 9 muffins left.

12 Trading cards ★★★

Solve \(9+\square=16\). Subtract: \(16-9=7\). Check: \(9+7=16\).

Leo needs 7 more cards.

13 Three addends, two ways ★★★

1. \(5+5=10\), then \(10+8=18\).
2. \(6+4=10\), then \(10+7=17\).

14 Pairs ★★★

\(8+8=16\), so \(9+8=17\). The number 17 ends in 7, so it is odd. It has one counter left over when you make pairs.

15 Think addition ★★★

1. \(9+7=16\), so \(16-9=7\).
2. \(8+6=14\), so \(14-8=6\).

16 Pick a strategy ★★★

Take 1 from the 7 to give to the 9: \(9+1=10\). What is left of 7 is 6. Then \(10+6=16\).

So \(7+9=16\).

17 Pairs that make 13 ★★★

Check each number: \(4+9=13\), \(5+8=13\), \(6+7=13\).

There are 3 pairs: 4 and 9, 5 and 8, 6 and 7.

18 At the zoo ★★★

First add: \(8+6+4\). Use \(6+4=10\), then \(10+8=18\).

Next subtract: \(18-9=9\).

9 animals are still outside.

19 Missing addend with three numbers ★★★

First add the known numbers: \(7+5=12\). Then \(12+\square=20\), so \(\square=20-12=8\).

Check: \(7+8+5=20\).

20 Number riddles ★★★

1. Think of a near double: \(7+8=15\). The numbers are 7 and 8.
2. \(9+10=19\). The numbers are 9 and 10.

21 Find the mistake ★★★

Check: \(6+7=13\), not 14. So Sam is wrong.

The right fact is \(6+8=14\), so \(14-6=8\).

22 Sharing fairly ★★★

15 is odd. When you make pairs, one cookie is left over, so they cannot share 15 equally.

14 is even. \(7+7=14\), so each friend gets 7 cookies.

23 Balance the equation ★★★

Find the right side first: \(6+8=14\). Then \(9+\square=14\), so \(\square=14-9=5\).

Check: \(9+5=14\).

24 Bus ride ★★★

After the first stop: \(9+7=16\). After the second stop: \(16-5=11\).

There are 11 children on the bus.