Quantitative Aptitude – Bar & Pie Charts
For the Meghalaya Police Constable Examination
1. Simple Explanation
| Chart | What it Shows | How it’s Drawn | Typical Use in Questions |
|---|---|---|---|
| Bar Chart | Discrete data – the height (or length) of each bar represents the quantity of a category. | Vertical bars (common) or horizontal bars. The y‑axis (or x‑axis) gives a numeric scale; the x‑axis lists the categories. | Find missing bars, totals, percentages, ratios, largest/smallest bar, differences. |
| Pie Chart | Parts of a whole – each slice’s angle is proportional to its percentage of the whole. | A circle divided into sectors. Each sector’s angle corresponds to the given percentage. | Find a missing percentage, actual value from a percentage, percentage from an actual value, ratios of slices. |
2. Key Points
| Bar Charts | Pie Charts |
|---|---|
| 1. Read the scale – the y‑axis is the most important key. | 1. Sum of all slices = 100 % (unless stated otherwise). |
| 2. Bar height = value – the longer the bar, the larger the quantity. | 2. Percentage × Total = Actual value. Actual = (Percent / 100) × Total |
| 3. Missing bars – use the given total or other relationships. | 3. Missing slice – subtract the sum of known slices from 100 %. |
| 4. Ratios of two bars – divide the heights of the two bars. | 4. Ratio of two slices – divide their percentages. |
5. Percentage of a bar – (Bar value / Total value) × 100. |
5. Percentage of a slice is given directly; if not, compute as above. |
| 6. Largest/Shrink – compare heights. | 6. Largest slice – highest percentage. |
7. Average of bars – Σ values / number of bars. |
7. Mean of percentages – Σ percentages / number of slices. |
| 8. Common pitfalls – wrong scale interpretation, ignoring units, mixing up ratio vs. percentage. | 8. Common pitfalls – forgetting that percentages must sum to 100 % (or the stated total), misreading “part |