Year 1: Arrays: rows and columns
Part of the Year 1 grouping and sharing chapter. Chapter overview · whole chapter on one page · Download worksheet (PDF) · Answers (PDF)
Arrays: rows and columns
An array is a neat set of things in rows and columns. A row goes across. A column goes down. Every row has the same number of things.
This tray has 3 rows with 4 biscuits in each row. Count the biscuits in each row and add them: 4 + 4 + 4 = 12.
Key ideas
- A row goes across.
- A column goes down.
- An array has the same number in each row.
- Turning an array round does not change how many things there are.
Key words. A row goes across. A column goes down. An array is things in rows and columns.
Method. Count the rows. Every row has the same number, so add that number once for each row.
- Count the rows. A row goes across.2 rows
- Count the things in one row. Every row has the same number.4 in each row
- Add one number for each row. Add the rows together.4 + 4 = 8
- Write the answer. 8
Check. Count down the columns too: 2 + 2 + 2 + 2 = 8. ✓
Watch out. Count each row once. Do not count a thing twice.
Key words. A row goes across. A column goes down. An array is things in rows and columns.
Method. Count the rows. Every row has the same number, so add that number once for each row.
- Count the rows. A row goes across.3 rows
- Count the things in one row. Every row has the same number.5 in each row
- Add one number for each row. Add the rows together.5 + 5 + 5 = 15
- Write the answer. 15
Check. Count down the columns too: 3 + 3 + 3 + 3 + 3 = 15. ✓
Watch out. Count each row once. Do not count a thing twice.
Key words. A row goes across. A column goes down. An array is things in rows and columns.
Method. Count the rows. Every row has the same number, so add that number once for each row.
- Count the rows. A row goes across.4 rows
- Count the things in one row. Every row has the same number.2 in each row
- Add one number for each row. Add the rows together.2 + 2 + 2 + 2 = 8
- Write the answer. 8
Check. Count down the columns too: 4 + 4 = 8. ✓
Watch out. Count each row once. Do not count a thing twice.
Watch out
Watch out: count each thing once. Count one row at a time, then add the rows, so you do not miss any.
Exam tip
Grown-up tip. Use an egg box or an ice cube tray. Ask: “How many rows? How many in each row? How many altogether?” Then turn the box round and ask the same questions again.
Exercise 9D Arrays
Non-calculatorKey words. A row goes across. A column goes down. An array is things in rows and columns.
Method. Count the rows. Every row has the same number, so add that number once for each row.
- Count the rows. A row goes across.2 rows
- Count the things in one row. Every row has the same number.4 in each row
- Add one number for each row. Add the rows together.4 + 4 = 8
- Write the answer. 8
Check. Count down the columns too: 2 + 2 + 2 + 2 = 8. ✓
Watch out. Count each row once. Do not count a thing twice.
Key words. A row goes across. A column goes down. An array is things in rows and columns.
Method. Count the rows. Every row has the same number, so add that number once for each row.
- Count the rows. A row goes across.3 rows
- Count the things in one row. Every row has the same number.3 in each row
- Add one number for each row. Add the rows together.3 + 3 + 3 = 9
- Write the answer. 9
Check. Count down the columns too: 3 + 3 + 3 = 9. ✓
Watch out. Count each row once. Do not count a thing twice.
Key words. A row goes across. A column goes down. An array is things in rows and columns.
Method. Count the rows. Every row has the same number, so add that number once for each row.
- Count the rows. A row goes across.5 rows
- Count the things in one row. Every row has the same number.2 in each row
- Add one number for each row. Add the rows together.2 + 2 + 2 + 2 + 2 = 10
- Write the answer. 10
Check. Count down the columns too: 5 + 5 = 10. ✓
Watch out. Count each row once. Do not count a thing twice.
Method. Count the rows. Each one is counted once.
- Count the rows. Touch each one once.1, 2, 3
- Look at the last number you said. That is how many rows there are.The last number is 3.
- Write the answer. 3 rows
Check. Count the rows from the other side. You get 3 again. ✓
Watch out. Count the rows, not the things inside them.
Method. Count the things in one row. Every row is the same, so one row tells us about all of them.
- Look at one row. Count the things in it.One row has 5
- Check the other rows. Each row has the same number.All 3 rows have 5
- Write the answer. 5
Check. Count one row again: 1, 2, 3, 4, 5. ✓
Watch out. Check that every row is the same before you use one of them.
Key words. A row goes across. A column goes down. An array is things in rows and columns.
Method. Count the rows. Every row has the same number, so add that number once for each row.
- Count the rows. A row goes across.3 rows
- Count the things in one row. Every row has the same number.5 in each row
- Add one number for each row. Add the rows together.5 + 5 + 5 = 15
- Write the answer. 15
Check. Count down the columns too: 3 + 3 + 3 + 3 + 3 = 15. ✓
Watch out. Count each row once. Do not count a thing twice.
Method. Count the biscuits in both trays. Turning a tray round does not change the total.
- Count the first tray. Two rows of 5.5 + 5 = 10
- Count the second tray. Five rows of 2. It is the first tray turned round.2 + 2 + 2 + 2 + 2 = 10
- Compare the totals. Both totals are the same.10 = 10
- Write the answer. Yes. Both trays have 10 biscuits.
Check. Count the biscuits in each row and each column. Both give 10. ✓
Watch out. Turning a tray round does not add or take away any biscuits.
Key words. A row goes across. A column goes down. An array is things in rows and columns.
Method. Count the rows. Every row has the same number, so add that number once for each row.
- Count the rows. A row goes across.2 rows
- Count the things in one row. Every row has the same number.3 in each row
- Add one number for each row. Add the rows together.3 + 3 = 6
- Write the answer. 6
Check. Count down the columns too: 2 + 2 + 2 = 6. ✓
Watch out. Count each row once. Do not count a thing twice.
Key words. Equal groups have the same number of eggs in each group.
Method. Add the same number 2 times, once for each group. Each group has 6.
- Write one 6 for each group. There are 2 groups, so there are 2 numbers to add.6 + 6
- Add the numbers together. Count in 6s to add them up: 6, 12.6 + 6 = 12
- Write the answer. 12
Check. Count in 6s: 6, 12. The last number is 12. ✓
Watch out. Write one number for every group. Do not write the number of groups instead.
Key words. A group is a set of things that belong together.
Method. Put 5 in each group, and keep going until none are left. Then count the groups.
- Make a group with 5 chairs. Each group must have the same number.1 group of 5
- Keep making groups until none are left. There are 10 in all, so count the groups as you make them.5 + 5 = 10
- Count the groups. Each group is one group.2 groups
Check. Each group has 5, and 2 groups make 10. ✓
Watch out. Count the groups, not the chairs. There are 2 groups.
Method. Write one number for each row, then add them.
- Count the rows. There are 4 rows.4 rows
- Count the biscuits in each row. Each row has 2 biscuits.2 in each row
- Write the addition. Add one 2 for each row.2 + 2 + 2 + 2 = 8
- Write the answer. 2 + 2 + 2 + 2 = 8
Check. Count in 2s: 2, 4, 6, 8. The last number is 8. ✓
Watch out. Write one number for each row, not for each biscuit.
Method. Count the biscuits on the tray. Then check Ali and Jo.
- Count the rows. There are 2 rows.2 rows
- Count the biscuits in each row. Each row has 6 biscuits.6 in each row
- Add the rows. Add the two rows together.6 + 6 = 12
- Write the answer. Ali is right. Jo counted only one row.Ali is right. There are 12 biscuits.
Check. Count every row, and the total is 12. ✓
Watch out. Count every row. Jo counted only one row.
Method. Count the things in both arrays. Then explain why they match.
- Count the first array. 3 rows of 4 make 12.4 + 4 + 4 = 12
- Count the second array. 4 rows of 3 make 12.3 + 3 + 3 + 3 = 12
- Compare them. It is the same things, turned round.12 = 12
- Write the answer. Both have 12 things. Turning the array round does not change the total.
Check. Count the things in both arrays. Both give 12. ✓
Watch out. The rows and columns swap over, but the number of things stays the same.