A bar graph has a scale of 5 (each gridline = 5 students). The bar for 'soccer' reaches the 6th gridline. How many students chose soccer?
A6 students — the bar reaches the 6th line
B30 students — because 6 × 5 = 30
C11 students — because 6 + 5 = 11
D15 students — because the scale adds 5 per bar
The scale tells you what each gridline represents. If each unit = 5, then a bar at the 6th gridline represents 6 × 5 = 30. Reading the bar height as a face value (6) is the most common error on scaled bar graphs — it ignores the scale entirely.
Question 2 Multiple Choice
On a scaled bar graph where each unit = 10, the 'red' bar reaches halfway between the 30 and 40 gridlines, and the 'blue' bar reaches the 50 gridline. How many more students chose blue than red?
A15 more — because 50 − 35 = 15
B10 more — the bars differ by one full gridline
C20 more — because 50 − 30 = 20
D5 more — they differ by half a unit
Halfway between 30 and 40 on a scale-of-10 graph is 35. Blue = 50. The difference is 50 − 35 = 15. Option B ignores the halfway position. Option C ignores the halfway position and rounds down. Once you convert bar heights to real values using the scale, the comparison is ordinary subtraction.
Question 3 True / False
On a bar graph where each unit equals 5, a bar that reaches the 4th gridline represents 4 students.
TTrue
FFalse
Answer: False
A bar at the 4th gridline represents 4 × 5 = 20 students, not 4. The gridline number must be multiplied by the scale to get the actual value. Reading bar height as face value only works when the scale is 1.
Question 4 True / False
The main reason to use a scale greater than 1 on a bar graph is to make large data sets fit into a readable, practical chart.
TTrue
FFalse
Answer: True
Scaling compresses large numbers visually. A graph showing 340 students at scale = 1 would need a 340-unit axis. At scale = 10, the same data fits in 34 units. The visual relationships between bars are preserved; only the labeling changes. Scaling doesn't distort the data — it makes it manageable.
Question 5 Short Answer
What is the first thing you should do before reading any bar on a scaled bar graph, and why?
Think about your answer, then reveal below.
Model answer: Identify the scale — find out what value each gridline unit represents. Without knowing the scale, you cannot convert bar height into an actual quantity.
The same bar height means completely different values depending on the scale. A bar at height 4 means 4 students at scale=1, 20 students at scale=5, and 40 students at scale=10. The scale is the key that unlocks the numbers. Always read it first — it's usually labeled on the y-axis or in a legend.