Do you remember the ‘What Can A Strip Say?’ activity from last year? In each strip, if we club the tiny strips belonging to each activity together, will we get a 100% stacked bar chart like the one in the figure?
Answer: Yes. Each strip is one whole day (24 hours). Joining the small pieces of the same activity keeps the total length and gives one piece per activity whose length is that activity’s share of the day: a 100% stacked bar. Several people’s strips side by side make a chart like the age-group chart.
Step-by-step solution
Idea: Moving pieces around inside a strip does not change its total length. Grouping by activity just reorders the pieces.
- A day-strip shows the day in time order, so the same activity (for example sleep) appears in several small pieces. Clubbing those pieces together gives one piece per activity, with length = total time on that activity.1 mark
- The whole strip still stands for 24 hours, and every person’s strip has the same length. So each strip becomes a bar split by shares of the day: a 100% stacked bar. Putting strips of several people (or groups) side by side gives a chart like the age-group chart (see the diagram). Only the time order of the day is lost.1 mark
Yes. Clubbing the pieces of each activity turns each 24-hour strip into one bar split into shares of the day, which is a 100% stacked bar; strips for several people give a chart like the age-group chart. What is lost is the order in which the activities happened.
Answer to write in the exam
Each strip = 24 h (same length for everyone)
Clubbing pieces of one activity: length = total time on it
Strip becomes one bar split by shares of the day
∴ Yes, we get a 100% stacked bar chart (the time order is lost)
Common mistakes that cost marks
- Thinking clubbing changes the total. The total stays 24 hours.
- Expecting the clubbed bar to show when each activity happened; it shows only how much.
- Forgetting that the bars of different people must all represent the same 24 hours to compare shares.
How this can come in the exam
Short answer (2 marks)
A strip shows a day as: sleep 6 h, school 6 h, play 2 h, homework 2 h, family time 2 h, sleep 2 h, travel 2 h, meals 2 h. Club the activities and give the share of sleep.
Show answer
Sleep = 6 + 2 = 8 h (1 mark). Share = 824 × 100 ≈ 33.3% (1 mark).Try one yourself
In a day-strip, reading appears in pieces of 1 h, ½ h and 1½ h. What is reading’s share of the day after clubbing?
Show answer
3 h of 24 h = 12.5%.
More questions like this
- The smart watch data of 5 people was tracked from Monday to Friday. The recorded data tells us how many hours each person spent lying down, sitting, and standing or moving around, etc., as shown in the following table.
- 1. Will the bars look similar if a different teacher’s data is considered instead of Zakir’s?
2. Will the bars look different if the data for all 7 days of the week is considered?
3. Some bars in the chart may also match people doing other kinds of work/activities. Can you think of any? Discuss. - In cricket, the run rate is the average number of runs scored per over. In a T20 match, a team scored 6 runs in the first over making the run rate 6.
- Five friends who play badminton surveyed the city and collected the price of shuttlecocks across brands and types (Nylon and Feather). The following is the list of the prices, in rupees (₹), that each one compiled.
Yusuf: 40(N), 105(N), 383(F), 108(N), 165(F), 116(F)
Srikanth: 194(N), 85(N), 93(N), 121(N)
Kashvi: 49(N), 297(F), 105(N), 275(F), 40(N)
Prasanna: 124(N), 333(F), 182(N), 258(F)
Gracy: 220(F), 458(F), 129(F), 183(N)
Can you describe a way they can work together to find the average price of a shuttlecock across types? - Shreyas holds 25 shares of a company at an average price of ₹150 and Vaishnavi holds 5 shares of the same company at an average price of ₹150.