The average category-wise daily electricity consumption of a house, in kWh, in 2005 and 2025 is shown in the table below. The corresponding stacked bar chart is also shown. Make the corresponding 100% stacked bar chart.
Step-by-step solution
| Lighting | Cooling | Kitchen appliances | Other appliances | |
|---|---|---|---|---|
| 2005 | 360 | 300 | 120 | 220 |
| 2025 | 220 | 800 | 460 | 520 |
Idea: In a 100% stacked bar, each bar stands for its own total (100%). Each piece’s length is its percentage of that total: parttotal × 100.
- 2005 total = 360 + 300 + 120 + 220 = 1000 units. Shares: lighting 3601000 × 100 = 36%, cooling 30%, kitchen appliances 12%, other appliances 22%.1 mark
- 2025 total = 220 + 800 + 460 + 520 = 2000 units. Shares: lighting 2202000 × 100 = 11%, cooling 8002000 × 100 = 40%, kitchen 4602000 × 100 = 23%, other 5202000 × 100 = 26%.1 mark
- Draw two bars of the same length on a 0%–100% scale and split them: 2005 at 36%, 66%, 78%, 100%; 2025 at 11%, 51%, 74%, 100% (diagram).1 mark
Check: 36 + 30 + 12 + 22 = 100 ✓ and 11 + 40 + 23 + 26 = 100 ✓.
Answer to write in the exam
2005: total = 360 + 300 + 120 + 220 = 1000
Lighting = 3601000 × 100 = 36%, cooling = 30%, kitchen = 12%, other = 22%
2025: total = 220 + 800 + 460 + 520 = 2000
Lighting = 2202000 × 100 = 11%, cooling = 40%, kitchen = 23%, other = 26%
∴ Two equal bars divided as 36 : 30 : 12 : 22 and 11 : 40 : 23 : 26
Common mistakes that cost marks
- Dividing the 2025 values by 1000 (the 2005 total). Each year uses its own total.
- Drawing the 2025 bar twice as long as the 2005 bar. In a 100% chart all bars have the same length.
- Percentages that do not add up to 100 because of a slip; always check the sum.
How this can come in the exam
A house uses 150 units for cooling out of 600 units in a month. In a 100% stacked bar, the cooling piece is
- 15%
- 25%
- 40%
- 150%
Show answer
(B) 25%
150600 × 100 = 25%.
A shop’s sales were: pens 120, notebooks 200, bags 80. Find the percentages for a 100% stacked bar.
Show answer
Total = 400 (½ mark). Pens 30%, notebooks 50%, bags 20% (1½ marks).Try one yourself
A family’s water use (litres per day) is: bathing 150, cooking 60, washing 90. Find the shares for a 100% stacked bar.
Show answer
Total 300: bathing 50%, cooking 20%, washing 30%.
More questions like this
- What do you observe? What do you find interesting in the data/graphs? Discuss with others.
- The 100% stacked bar below compares the proportion of flowers blooming in Fatima’s garden and Naveen’s garden across seasons. Which of the following statements can be inferred from this chart?
(Hint: Find out the blooms per season in each garden if both the gardens had the same total number of blooms over the year. Similarly find out what happens if the totals are very different.) - 1. What does this say about the scope of the stacked bars and 100% stacked bars?
2. Given a stacked bar chart can we make a corresponding 100% stacked bar chart?
3. Given a 100% stacked bar chart can we make a corresponding stacked bar chart?
4. What kind of inferences or comparisons can be made from a stacked bar chart and in a 100% stacked bar chart? - The following chart shows the time spent on different activities in a day by the average Indian. What do you notice? What do you wonder about?
- 1. What do you find interesting in the chart above? What can you infer? Discuss.
2. Do you remember the sleep time over age trend that you studied last year? Does that trend align with this chart?
3. Can you explain why the learning time of people in the age group 15 – 24 has reduced significantly compared to that of the age group 6 – 14?
4. Do adults spend about an equal amount of time in paid and unpaid work? What do you think?