Year 2 Multiplying and dividing: check-up and quiz

Key words. Equal groups have the same number of things in each group.

Method. Add the same number once for each group. Count the groups first.

1. Look at one group. Each group has 7 marbles.
   7 in one group
2. Add the same number once for each group. There are 2 groups, so add 7 2 times.
   7 + 7
3. Write the total. The total is 14 marbles.
   14

Check. Count in 7s: 7, 14. ✓

Watch out. Count the groups first. Then add one number for each group.

Method. Count the rows. Then add the number in one row, once for each row.

1. Count the rows. There are 4 rows.
   4 rows
2. Count the things in one row. Each row has 2 hats.
   2 in each row
3. Add the rows. Add 2 once for each row.
   2 + 2 + 2 + 2 = 8

Check. Count down the columns too. Both ways make 8. ✓

Watch out. Rows go across. Columns go down. Count each row once, and do not skip any.

Method. Write the groups as a sum with the sign ×, then work out the total.

1. Read the groups. There are 5 groups of 3.
   5 groups of 3
2. Write it with the sign ×. The sign × means groups of.
   5 × 3
3. Work out the total. Add 3, 5 times.
   5 × 3 = 15

Check. 3 + 3 + 3 + 3 + 3 = 15. ✓

Watch out. The first number says how many groups. The second says how many in each group.

Method. Write the sharing as a sum with the sign ÷.

1. Share the things equally. Put 12 things into 2 equal groups.
   12 shared into 2 groups
2. Count what is in one group. Each group has 6.
   6 in each group
3. Write it with the sign ÷. The sign ÷ means share into equal groups.
   12 ÷ 2 = 6

Check. Add 6, 2 times: 6 + 6 = 12. ✓

Watch out. The number being shared comes first. The number of groups comes second.

Key words. Equal groups have the same number of things in each group.

Method. Add the same number once for each group. Count the groups first.

1. Look at one group. Each group has 2 socks.
   2 in one group
2. Add the same number once for each group. There are 9 groups, so add 2 9 times.
   2 + 2 + 2 + 2 + 2 + 2 + 2 + 2 + 2
3. Write the total. The total is 18 socks.
   18

Check. Count in 2s: 2, 4, 6, 8, 10, 12, 14, 16, 18. ✓

Watch out. Count the groups first. Then add one number for each group.

Key words. Equal groups have the same number of things in each group.

Method. Add the same number once for each group. Count the groups first.

1. Look at one group. Each group has 5 stars.
   5 in one group
2. Add the same number once for each group. There are 7 groups, so add 5 7 times.
   5 + 5 + 5 + 5 + 5 + 5 + 5
3. Write the total. The total is 35 stars.
   35

Check. Count in 5s: 5, 10, 15, 20, 25, 30, 35. ✓

Watch out. Count the groups first. Then add one number for each group.

Key words. Equal groups have the same number of things in each group.

Method. Add the same number once for each group. Count the groups first.

1. Look at one group. Each group has 10 things.
   10 in one group
2. Add the same number once for each group. There are 8 groups, so add 10 8 times.
   10 + 10 + 10 + 10 + 10 + 10 + 10 + 10
3. Write the total. The total is 80 things.
   80

Check. Count in 10s: 10, 20, 30, 40, 50, 60, 70, 80. ✓

Watch out. Count the groups first. Then add one number for each group.

Key words. An even number makes pairs. An odd number has one left over.

Method. Put the things into pairs. Look for one left over.

1. Make pairs. Put the 17 things into pairs.
   8 pairs
2. Look for one left over. 8 pairs and 1 left over.
   1 left over
3. Write the answer. A number with one left over is odd.
   odd

Check. 8 pairs make 16. 17 is odd. ✓

Watch out. Odd numbers have one left over. Even numbers have none left over.

Method. Work out both ways. If the answers match, the order does not matter.

1. Work out the first way. 4 groups of 6 is 24.
   4 × 6 = 24
2. Swap the numbers and work out the other way. 6 groups of 4 is also 24.
   6 × 4 = 24
3. Compare the answers. The two answers are the same, so the order does not matter.
   Yes. 4 × 6 = 6 × 4

Check. Both ways make 24. Count the array the other way to check. ✓

Watch out. Multiplication works in any order. Division does not.

Key words. Equal groups have the same number of things in each group.

Method. Add the same number once for each group. Count the groups first.

1. Look at one group. Each group has 5 sweets.
   5 in one group
2. Add the same number once for each group. There are 6 groups, so add 5 6 times.
   5 + 5 + 5 + 5 + 5 + 5
3. Write the total. The total is 30 sweets.
   30

Check. Count in 5s: 5, 10, 15, 20, 25, 30. ✓

Watch out. Count the groups first. Then add one number for each group.

Key words. Equal groups have the same number of things in each group.

Method. Add the same number once for each group. Count the groups first.

1. Look at one group. Each group has 2 shoes.
   2 in one group
2. Add the same number once for each group. There are 6 groups, so add 2 6 times.
   2 + 2 + 2 + 2 + 2 + 2
3. Write the total. The total is 12 shoes.
   12

Check. Count in 2s: 2, 4, 6, 8, 10, 12. ✓

Watch out. Count the groups first. Then add one number for each group.

Key words. Equal groups have the same number of things in each group.

Method. Add the same number once for each group. Count the groups first.

1. Look at one group. Each group has 10 things.
   10 in one group
2. Add the same number once for each group. There are 9 groups, so add 10 9 times.
   10 + 10 + 10 + 10 + 10 + 10 + 10 + 10 + 10
3. Write the total. The total is 90 things.
   90

Check. Count in 10s: 10, 20, 30, 40, 50, 60, 70, 80, 90. ✓

Watch out. Count the groups first. Then add one number for each group.

Key words. Equal groups have the same number of things in each group.

Method. Add the same number once for each group. Count the groups first.

1. Look at one group. Each group has 8 stars.
   8 in one group
2. Add the same number once for each group. There are 5 groups, so add 8 5 times.
   8 + 8 + 8 + 8 + 8
3. Write the total. The total is 40 stars.
   40

Check. Count in 8s: 8, 16, 24, 32, 40. ✓

Watch out. Count the groups first. Then add one number for each group.

Method. Make groups of the same size, then count how many groups there are.

1. Make groups of the same size. Put 2 socks in each group.
   2 in each group
2. Count the groups. Keep making groups until none are left. There are 8 groups.
   8 groups
3. Write the answer. 16 ÷ 2 means how many groups of 2.
   8

Check. Count in 2s: 2, 4, 6, 8, 10, 12, 14, 16. ✓

Watch out. Count the groups, not the things in each group.

Method. Make groups of the same size, then count how many groups there are.

1. Make groups of the same size. Put 5 stars in each group.
   5 in each group
2. Count the groups. Keep making groups until none are left. There are 3 groups.
   3 groups
3. Write the answer. 15 ÷ 5 means how many groups of 5.
   3

Check. Count in 5s: 5, 10, 15. ✓

Watch out. Count the groups, not the things in each group.

Key words. An even number makes pairs. An odd number has one left over.

Method. Put the things into pairs. Look for one left over.

1. Make pairs. Put the 21 things into pairs.
   10 pairs
2. Look for one left over. 10 pairs and 1 left over.
   1 left over
3. Write the answer. A number with one left over is odd.
   odd

Check. 10 pairs make 20. 21 is odd. ✓

Watch out. Odd numbers have one left over. Even numbers have none left over.

Method. Count in 5s. Count how many jumps you need.

1. Count in the known number. Count in 5s until you reach 35.
   5, 10, 15, 20, 25, 30, 35
2. Count the jumps. It takes 7 jumps to reach 35.
   7 jumps
3. Write the missing number. The missing number is the number of jumps.
   7

Check. 5 × 7 = 35. ✓

Watch out. The missing number is how many times you say the number, not the total.

Method. Work out what the sum means, then choose the sign.

1. Read the sum. 24 and 4 have a sign missing.
   24 ? 4 = 6
2. Think what the sign means. Share 24 into 4 equal groups: 6 in each group.
   24 ÷ 4 = 6
3. Write the sign. The sign ÷ means share into equal groups.
   ÷

Check. 24 ÷ 4 = 6. ✓

Watch out. Groups of is ×. Share into groups is ÷.

Method. Work out both ways. If the answers match, the order does not matter.

1. Work out the first way. 5 groups of 3 is 15.
   5 × 3 = 15
2. Swap the numbers and work out the other way. 3 groups of 5 is also 15.
   3 × 5 = 15
3. Compare the answers. The two answers are the same, so the order does not matter.
   Yes. 5 × 3 = 3 × 5

Check. Both ways make 15. Count the array the other way to check. ✓

Watch out. Multiplication works in any order. Division does not.

Key words. Equal groups have the same number of things in each group.

Method. Add the same number once for each group. Count the groups first.

1. Look at one group. Each group has 4 books.
   4 in one group
2. Add the same number once for each group. There are 6 groups, so add 4 6 times.
   4 + 4 + 4 + 4 + 4 + 4
3. Write the total. The total is 24 books.
   24

Check. Count in 4s: 4, 8, 12, 16, 20, 24. ✓

Watch out. Count the groups first. Then add one number for each group.