A bar graph has a scale where each grid line represents 5 students. The bar for 'cats' reaches the 4th grid line. How many students chose cats?
A4, because the bar reaches the 4th line
B9, because 4 + 5 = 9
C20, because 4 × 5 = 20
D45, because you multiply the scale by the number of bars
When the scale says each grid line equals 5, you multiply the line number by the scale value: 4th line × 5 = 20. The most common error (option A) is forgetting the scale entirely and treating each grid line as 1 unit — this is precisely what the scale key is there to prevent.
Question 2 Multiple Choice
On a scaled bar graph (scale: each line = 10), the 'soccer' bar reaches 40 and the 'basketball' bar reaches 25. How many MORE students chose soccer than basketball?
A65, by adding 40 + 25 to find the combined total
BCount how many bars are in the graph
C15, by subtracting 40 − 25
D1,000, by multiplying 40 × 25
'How many more' is a comparison question that requires subtraction: 40 − 25 = 15. Option A (addition) answers 'how many total,' which is a different question. Understanding which operation matches which question type is essential — misreading 'more' as 'total' is the most common error on comparison questions.
Question 3 True / False
Before reading any bar in a scaled bar graph, you should always check the scale on the axis to know what each grid line represents.
TTrue
FFalse
Answer: True
Checking the scale first is the foundational habit for scaled bar graphs. Every reading error traces back to ignoring or misremembering the scale. If the scale is 5, a bar on the 3rd line is 15, not 3. Making scale-checking automatic prevents systematic errors across all readings.
Question 4 True / False
In a scaled bar graph where each interval equals 5, a bar landing on the 3rd grid line represents 3 students.
TTrue
FFalse
Answer: False
A bar on the 3rd grid line represents 3 × 5 = 15 students, not 3. Reading the grid-line number directly (treating each line as 1) is the classic error on scaled bar graphs. You must always multiply the position by the scale value.
Question 5 Short Answer
A classmate says, 'I just count how many squares tall the bar is.' What is the problem with this approach on a scaled bar graph, and what should they do instead?
Think about your answer, then reveal below.
Model answer: Counting squares only works if each square represents 1 unit. On a scaled bar graph, each grid interval represents more than 1 (for example, 5 or 10). To read correctly, you must find where the bar ends on the axis and multiply that position by the scale value. Always check the scale key first so you know what one interval equals.
The scale key transforms a raw bar-length count into a meaningful data value. Without applying it, every reading will be wrong by a fixed factor (the scale). The habit of checking the scale before reading any bar is the core skill this topic develops.