Bar Graphs

Bar graphs show quantities as bar heights, making comparisons visual. They are a common placement DI format, often as grouped or stacked bars comparing categories across years.

Method

• Read the axis scale and units before reading any bar.
• Simple bars compare single values; grouped bars compare sub-categories side by side; stacked bars split one bar into parts.
• Apply the same tools: totals, differences, percentage change, ratios.

Bar type	Shows
Simple	one value per category
Grouped	sub-categories side by side
Stacked	components summing to a whole
Reading	height × axis scale = value

Example: if a bar reaches 60 on a scale marked in units of 10, its value is 60; a bar at 45 is 25% lower than one at 60. (15/60 = 25%.) ✓

Exam Tricks & Tips

• 🎯 Note the axis SCALE first — bars mean nothing without units.
• 🎯 For grouped bars, track which colour/pattern is which sub-category.
• 🎯 Stacked bars: read the segment length, not the top position, for a component.
• 🎯 "Percentage more/less" compares two bar values over the base bar.
• 🎯 Estimate heights between gridlines rather than guessing wildly.
• ❌ Don't compare bars from charts with different scales as if equal.

Expected exam pattern: compare categories, percentage difference between bars, and totals across grouped/stacked bars. 3 to 5 questions, ~50 seconds each.

Quick recap: read the scale, identify the bar type, read heights as value = height × scale, and apply percentage/ratio as usual.

Q1. What does a bar's height represent?
A1. Its value = height × the axis scale.

Q2. First thing to check on a bar graph?
A2. The axis scale and units.

Q3. Grouped bars show?
A3. Sub-categories side by side.

Q4. Stacked bars show?
A4. Components summing to a whole.

Q5. A bar at 45 vs one at 60 — percentage lower?
A5. 15/60 = 25%.

Q6. For a stacked component, read the?
A6. Segment length, not the top position.

Q7. Risk when comparing two charts?
A7. Different scales making bars non-comparable.

Q8. "Percentage more" compares over which value?
A8. The base bar's value.

Q9. How to read between gridlines?
A9. Estimate proportionally, don't guess wildly.

Q10. Simple bar shows?
A10. One value per category.

Q11. Value of a bar reaching 60 on a scale of 10s?
A11. 60.

Q12. What must you track in grouped bars?
A12. Which colour/pattern is which sub-category.

Bar graphs turn numbers into heights, so the questions add a layer of reading values off an axis. The winning habit is to read each bar's value once, jot it down, and then treat the problem like a table.

What this topic tests: reading single, grouped and stacked bar charts and computing comparisons, totals and percentage changes.

The method

Beginner — read values onto paper

Note the axis scale (each gridline's value) and read each relevant bar's height. Write the numbers down — working from a small table of values you extracted is far less error-prone than repeatedly eyeballing bars.

Intermediate — grouped and stacked bars

• Grouped (clustered) bars: each category has several bars side by side (e.g. two years). Compare within a group or across groups.
• Stacked bars: segments sit on top of each other and the total is the full height; a segment's value is the difference between its top and the segment below. To read the middle segment, subtract the lower boundary from the upper.

Advanced — comparisons and estimation

• For "percentage increase/decrease", use (new − old)/old × 100 on the read values.
• For "which category is highest/lowest", compare bar heights directly — no computation needed.
• Estimate when a bar falls between gridlines; MCQ options are usually far enough apart that a close read suffices.

Worked example

A grouped bar chart shows sales (units): Product A — 2022: 300, 2023: 375; Product B — 2022: 400, 2023: 360. Which product grew, and by what percent?
Product A: (375 − 300)/300 = 75/300 = +25%. Product B fell (400 → 360 = −10%). So A grew by 25%, B declined.

Where it appears

TCS NQT, Infosys, Wipro, Cognizant, Capgemini DI; bar graphs are a frequent DI set, often paired with a table.

Speed tricks and shortcuts

• Extract bar values to a mini-table first, then compute.
• Stacked bar segment = upper boundary − lower boundary.
• Compare heights directly for max/min questions.
• Mnemonic: "Read once, write it down, then it's just a table."

Key formulas

• Read bar heights; difference of heights = absolute change.
• Growth% = (later − earlier)/earlier ×100.
• Average height = sum of values/number of bars.
• Stacked bars: segment = category value; total = full bar.
• Compare groups by ratio of heights.

Usage: for grouped/stacked bars, separate the segments before comparing.

Worked Example

Problem: A bar graph shows the number of cars sold by a dealer over five months (each bar's height given below).

Month	Jan	Feb	Mar	Apr	May
Cars sold	40	55	35	60	50

The number of cars sold in April was what percentage of the total sold over the five months?

Solution: Read the April bar: 60 cars.

Find the total over all five bars:
40 + 55 + 35 + 60 + 50 = 240.

Required percentage = (April / total) × 100 = (60 / 240) × 100 = 25%.

Answer: 25%.