M2.5.8 Chapter 8
Grids and directions
How do I tell a friend which box to look in?
Your guess
Pick one before you read on. It is fine to be wrong.
By the end you can
- Give a position on a grid by column and row
- Use north, south, east and west to describe a route
A grid is a set of boxes in rows and columns. It names a place exactly.
Draw it first
Find the box B3
1 Letters name the boxes across. Numbers name the boxes down.
2 A column goes up and down. This is column B.
3 A row goes across. This is row 3.
4 Column B and row 3 meet in one box. Its name is B3.
Say the column first, then the row. B3 means column B, row 3.
Maps show direction too. North is at the top of a map. South is at the bottom.
East is on the right. West is on the left. These four are the compass points.
Face north. East is on your right. West is on your left. South is behind you.
To find north where you live, use a map or a compass. Ask a neighbour if you are not sure.
A route is the path you follow from one box to another. Say it in boxes and compass points.
Worked example
Start at A1. Go east 3 boxes. Then go south 2 boxes. Which box are you in?
- East is to the right, along the letters. From A, go 3 boxes: B, C, D.
- You are in column D. You are still in row 1.
- South is down, along the numbers. From row 1, go 2 boxes: 2, 3.
- Column D and row 3 make the box D3.
Answer: D3
See it three ways
With things
Draw a grid on paper. Put a bean in one box. Tell a friend its name, column first.
As a picture
In symbols
The well is in column C and row 3. Its name is C3.
Try it
Walk a route on a floor grid
You need: floor tiles, or chalk or a stick for drawing boxes, a stone to mark north.
- Make a grid 4 boxes wide and 4 boxes long.
- Put the stone by one edge. That edge is north, like the top of a map.
- Face the stone. Write A to D along that edge, from left to right.
- Write 1 to 4 along a side. Start next to the stone. East is on your right.
- Stand in B2. Walk east 2 boxes. Say your box. You are in D2.
- Walk south 1 box, then west 3 boxes. Say your box each time. You end in A3.
What you will see: Each step changes one thing. East and west change the column letter. North and south change the row number.
A wrong idea many people have
The order of a grid position does not matter.
Why it feels right: Adding can swap places. 2 + 3 and 3 + 2 are equal.
The test that breaks it: Draw a grid. Count 2 boxes across and 3 down. Mark the box. Now count 3 across and 2 down. Mark that box too. They are different boxes.
What is true: A position has a fixed order. Say the column first, then the row. 2 across and 3 down is B3. 3 across and 2 down is C2.
Key words
- column
- boxes in a line going up and down.
- row
- boxes in a line going across.
- compass points
- north, east, south and west.
- route
- the path you follow from one place to another.
Back to your guess
The answer is C: Say the column and the row, like B3.
A column alone names a whole stripe of boxes. A column and a row meet in one box. Everyone must say them in the same order. This book gives the column first.
Check yourself
Try each one before you look. A wrong answer tells you where to go next.
Which box has the well?
See the answer
C3
The well is in column C and row 3. Column first, then row, so C3.
- If you chose B: This book says the column letter comes first, then the row number. Write C3.
- If you chose C: Look at the letter above the well. It is C, not B. Box B3 is under the hut.
Start at B1. Go east 2 boxes. Then go south 3 boxes. Which box are you in?
See the answer
D4
East 2 from B is C, D. South 3 from row 1 is 2, 3, 4. So you are in D4.
Mei is in box E3. She walks west 2 boxes. Which box is she in?
See the answer
C3
West is left, along the letters. From E, go back 2 boxes: D, C. The row stays 3.
You face north. Where is east?
See the answer
On your right
Face north. East is on your right. West is on your left. South is behind you.
- If you chose B: West is on your left when you face north. East is the other side.
- If you chose C: South is behind you when you face north. East is to the side.
From an earlier chapter
Ravi faces north. He turns a quarter turn clockwise, so he faces east. How many degrees did he turn?
See the answer
90°
A quarter turn is one right angle. A full turn is 360°, and 360 ÷ 4 = 90.
Tariq is in box B2. He walks east 2 boxes. Which box is he in?
See the answer
D2
East is to the right, along the letters. From B, go 2 boxes: C, D. The row stays 2.
- If you chose A: You counted the box you stand in as 1. Step 2 boxes away from B: C, then D.
- If you chose B: That changes the row number. East and west change the letter. North and south change the number.
Ana walked from A1 to D3. She went east 3 boxes, then south 2 boxes. How does she walk back?
See the answer
North 2 boxes, then west 3 boxes
Going back, the last walk comes first. South 2 becomes north 2. Then east 3 becomes west 3.
- If you chose B: Those are the same directions as the way there. To go back, turn each direction round.
- If you chose C: The directions are right, but the numbers are swapped. She went south 2 boxes and east 3.
Which name tells where the dot is?
See the answer
D2
The dot is in column D. It is in row 2, counting down from the top. Column first, so D2.
- If you chose A: You read the row first. This book says the column letter comes first, then the row number.
- If you chose C: You counted the rows from the bottom. Rows are numbered from the top, so this is row 2.
Keep it
Copy this into your exercise book.
Name a box by column, then row: B3. North is up, east is right, south is down, west is left. East and west change the letter. North and south change the number.
Draw: A grid of 4 columns and 3 rows. Label it A to D and 1 to 3. Mark B2 with a dot.