IMOClass 3 › Data Handling

Data Handling

Collecting Data & Tally Marks

Data is information we collect, such as everyone's favourite colour or fruit. We can record counts using tally marks. Each mark is a line, and the fifth mark is drawn across the first four to make a group of 5.

To read tally marks, count the groups of 5 and add the extra lines.

Example 1: How many does one full group of tally marks stand for?
A group (four lines crossed by a fifth) stands for 5.
Example 2: One group of 5 and 2 more lines means how many?
5 + 2 = 7.
Quick recap
  • Tally marks record counts in groups of 5.
  • Read them by counting groups of 5 and adding extras.
✓ Quick check
Three tally lines (not crossed) stand for ___ ?
Three single lines mean 3.
One full group of 5 tally marks and 1 more line means ___ ?
5 + 1 = 6.

Pictographs

A pictograph shows data using pictures, where one picture stands for a fixed number of things. If 1 picture = 2 units, then 4 pictures mean 4 × 2 = 8.

We read a pictograph to find which row has the most or least, and to work out totals and differences.

Example 1: If 1 ⚽ stands for 2 goals, how many goals do 4 ⚽ show?
4 × 2 = 8 goals.
Example 2: Apples have 6 pictures and oranges 4 (1 picture = 1 fruit). Which is more?
Apples (6 > 4).
Quick recap
  • In a pictograph, one picture stands for a fixed number.
  • Multiply pictures by the value to read the count.
✓ Quick check
If 1 🍎 stands for 5 apples, how many apples do 3 🍎 show?
3 × 5 = 15 apples.
Mango has 7 pictures, apple 5 and banana 3 (1 picture = 1 fruit). Which sold the most?
Mango has the most pictures (7).

Bar Graphs

A bar graph shows data using bars of different heights. With a scale of 1 unit, the height of each bar gives its value. The tallest bar shows the most and the shortest bar shows the least.

We can add bar values for a total or subtract them to find a difference.

Example 1: In a bar graph, which bar shows the most?
The tallest bar shows the most.
Example 2: If one bar is 6 and another is 4, what is the difference?
6 − 4 = 2.
Quick recap
  • Taller bar = more; shorter bar = less.
  • Add bar values for a total; subtract for a difference.
✓ Quick check
In a bar graph, the longest bar shows the ___ ?
The longest (tallest) bar shows the most.
One bar shows 6 and another shows 4. What is the total?
6 + 4 = 10.
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