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Pie chart · finding the total
P6 · Data analysis · PSLE Maths
Question
The pie chart below shows the favourite after-school activities of the pupils in Class 6A. The sector for Football is a right angle. 20% of the pupils like Board Games and 15% like Arts and Crafts. The rest like Coding. Given that 6 pupils like Arts and Crafts, how many pupils are surveyed altogether? How many pupils like Coding?
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Hint
First change the right angle to 90° ÷ 360° = 1/4 = 25%, then find the percentage for Coding.
Show the answer and step-by-step explanation
Answer: Total number surveyed 40 pupils; Coding 16 pupils
- Read the chart — The whole circle in a pie chart represents all the pupils surveyed. Let us read the parts given in the chart first.
- Right angle — A right angle is 90°. A full circle is 360°, so Football is 1/4, or 25%.
- Express in units — Write 25%, 20% and 15% in twentieths: 25% = 5/20, 20% = 4/20, 15% = 3/20. So it is convenient to let the whole class be 20 units.
- Find the total — Arts and Crafts is 3 units, which is 6 pupils. So 1 unit = 2 pupils, and 20 units make 40 pupils.
- Find Coding — Coding is the remaining part: 20 − 5 − 4 − 3 = 8 units. 8 units = 8 × 2 = 16 pupils. 📌 Key idea: In a pie chart, change the parts to the same units, use the given part to find 1 unit, then find the total or the required part.
Method: A pie chart represents one whole. Change all parts to the same form, such as percentages or fractions. Find the unknown part, then use the given number of pupils for one part to find the total and the other part.
Practice: 3 similar questions
- A pie chart shows the favourite food of a group of P6 pupils. The sector for roti prata is a right angle, 30% like noodles, 20% like sandwiches, and the rest like fruit. Given that 10 pupils like fruit, how many pupils are there altogether? How many pupils like noodles?
Answer
40 pupils, 12 pupils — Roti prata is 25%. Fruit is 100% − 25% − 30% − 20% = 25%. 25% corresponds to 10 pupils, so the total number = 10 ÷ 25% = 40 pupils. Noodles are 30%, so the number = 30% × 40 = 12 pupils.
- Siti surveys how pupils travel to school. In the pie chart, the sector for walking is a right angle, 40% take the bus, 15% come by car, and the rest take the MRT. Given that 18 pupils take the bus, how many pupils are surveyed altogether? How many pupils take the MRT?
Answer
45 pupils, 9 pupils — Walking is 25%. MRT is 100% − 25% − 40% − 15% = 20%. 40% corresponds to 18 pupils, so the total number = 18 ÷ 40% = 45 pupils. Number who take the MRT = 20% × 45 = 9 pupils.
- Raju makes a pie chart about pupils' favourite types of books. The sector for mystery stories is a right angle, 35% like comics, 20% like science books, and the rest like adventure stories. The number of pupils who like comics is 15 more than those who like adventure stories. How many pupils are surveyed altogether? How many pupils like mystery stories?
Answer
100 pupils, 25 pupils — Mystery stories are 25%. Adventure stories are 100% − 25% − 35% − 20% = 20%. The difference between comics and adventure stories is 35% − 20% = 15%, and this 15% corresponds to 15 pupils. Total number = 15 ÷ 15% = 100 pupils. Number who like mystery stories = 25% × 100 = 25 pupils.
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