
Written solutions to the chapter problems. Check each step, then correct yourself.
1 Ducks on a pond ★★★
More ducks join, so we add: \(7 + 6 = 13\).
There are 13 ducks on the pond.
2 Popped balloons ★★★
Some balloons go away, so we subtract: \(15 - 8 = 7\).
Maya has 7 balloons left.
3 Red and blue marbles ★★★
Two groups are put together: \(9 + 4 = 13\).
There are 13 marbles in the bag.
4 Stickers on a page ★★★
The total is 12 and one part is 5, so we take apart: \(12 - 5 = 7\).
Check: \(5 + 7 = 12\). There are 7 stickers in the box.
5 True or false? ★★★
- True: \(6 + 7 = 13\).
- False: \(15 - 9 = 6\), not 7. Check: \(6 + 9 = 15\).
6 Seashells ★★★
We compare the two amounts: \(11 - 8 = 3\).
Mia found 3 more seashells than Leo. Check: \(8 + 3 = 11\).
7 Match the equation ★★★
Birds go away, so the equation is \(10 - 4 = 6\).
There are 6 birds left.
8 Apples in a bowl ★★★
The change is unknown: \(6 + ? = 14\).
\(14 - 6 = 8\). Check: \(6 + 8 = 14\). Dad put in 8 apples.
9 Frogs on a log ★★★
The start is unknown: \(? + 5 = 12\).
\(12 - 5 = 7\). Check: \(7 + 5 = 12\). There were 7 frogs at first.
10 Cookies ★★★
The start is unknown: \(? - 6 = 9\).
To find the start we add back what was taken: \(9 + 6 = 15\). Check: \(15 - 6 = 9\). There were 15 cookies.
11 Boys and girls ★★★
We take apart the total: \(17 - 9 = 8\).
Check: \(9 + 8 = 17\). There are 8 boys.
12 Fewer stickers ★★★
“Fewer” means a smaller amount: \(16 - 7 = 9\).
Ava has 9 stickers.
13 Crayon box ★★★
There is no pair that makes 10, so we add in order: \(5 + 7 = 12\), then \(12 + 4 = 16\).
There are 16 crayons.
14 Complete the bar model ★★★
The missing part is \(18 - 11 = 7\).
Equations: \(11 + 7 = 18\) and \(18 - 11 = 7\).
15 Add or subtract? ★★★
- More arrive: \(9 + 8 = 17\) cats.
- Some go away: \(18 - 9 = 9\) fish are left.
- Groups are put together: \(7 + 11 = 18\) children.
16 Find the missing number ★★★
- \(13 - 5 = 8\), so \(13 = 5 + 8\).
- The start is \(9 + 8 = 17\), so \(9 = 17 - 8\).
- \(14 - 6 = 8\), so \(14 - 8 = 6\).
- \(11 - 4 = 7\), so \(7 + 4 = 11\).
17 Pencils ★★★
Tom has the bigger amount, and the gap is 4. So Nia has \(9 - 4 = 5\) pencils.
Check: \(5 + 4 = 9\).
18 Make ten first ★★★
- \(8 + 2 = 10\), then \(10 + 6 = 16\).
- \(7 + 3 = 10\), then \(10 + 5 = 15\).
19 Birds on a wire ★★★
Step 1: \(9 + 5 = 14\) birds.
Step 2: \(14 - 7 = 7\) birds.
There are 7 birds on the wire now.
20 Find the mistake ★★★
People got off, so the number gets smaller. Max added, but he should subtract.
Right equation: \(14 - 6 = 8\). There are 8 people on the bus.
21 Compare with a model ★★★
The gap is \(16 - 11 = 5\). Raj has 5 fewer stickers.
Sample story: Nora has 8 toy cars. She gets 7 more. Now she has \(8 + 7 = 15\) toy cars.
Test yourself: quick challenge for Grade 1
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