Curriculum
GRADE VIII MATHS
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Square And Cube
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Power Play
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Story Of Numbers
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Quadrilaterals
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Number Play
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Distribute Mutiply
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Proportional Reasoning 1
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Fraction In Disguise
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Baudhayana-Pythagoras
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Proportional Reasoning 2
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Geometric Themes
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Dots And Lines
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Algebra Play
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Area
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Fraction In Disguise
School Revise · Grade 8 · Maths · Chapter 8 · Ganita Prakash
Fractions in Disguise
Mathematics, Class 8, Ganita Prakash. A percentage is just a fraction out of a hundred, wearing a disguise. This chapter converts between fractions, decimals and percentages, and finds percentage increase and decrease.
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What this chapter is about
Discounts, marks and interest are all given as percentages. In this chapter we see that a percentage is a fraction with denominator 100, learn to switch between fractions, decimals and percentages, and work out percentage change.
1. Percentage as a fraction
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Percentage a percentage is a fraction out of 100; x% means x/100 So 35% = 35/100 = 0.35. To find a percentage of an amount, multiply the amount by that fraction. A fraction becomes a percentage by making the denominator 100. In real life: A shop offering 35% off means 35 out of every 100 rupees is taken off the price. |
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Worked example 1 Question. Find 25% of 80.
Answer: 25% of 80 = 20. |
2. Switching forms and percentage change
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Converting and change a fraction × 100 gives a percentage; a percentage change is the change divided by the original, times 100 So 3/5 = 3/5 × 100 = 60%. If a price rises from 200 to 230, the increase is 30, and 30/200 × 100 = 15%. In real life: Comparing marks out of different totals is easy once each is turned into a percentage. |
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Worked example 2 Question. Convert 3/5 into a percentage.
Answer: 3/5 = 60%. |
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Worked example 3 Question. A price of ₹200 rises to ₹230. Find the percentage increase.
Answer: The increase is 15%. |
Practise with the interactive
Try it hands on: shade the hundred square to see a percentage, and convert freely between a fraction, a decimal and a percentage. The interactive opens right here in the lesson.
Practice set A, multiple choice
1. 50% of 60 is …
| 1 | 50% = 1/2. 1/2 × 60. |
| 2 | So. 30. |
2. 0.7 as a percentage is …
70%, since 0.7 = 70/100.
3. 1/4 as a percentage is …
| 1 | 1/4 × 100. = 25. |
| 2 | So. 25%. |
4. A price falls from 100 to 80. The percentage decrease is …
| 1 | Decrease is 20. 20/100 × 100. |
| 2 | So. 20%. |
Practice set B, short answer
1. Find 20% of 150.
| 1 | 20% = 1/5. 1/5 × 150. |
| 2 | So. 30. |
2. Convert 7/20 to a percentage.
| 1 | 7/20 × 100. = 35. |
| 2 | So. 35%. |
3. Marks rise from 40 to 50. Find the percentage increase.
| 1 | Increase is 10. 10/40 × 100. |
| 2 | So. 25%. |
Quick summary
| Idea | The idea |
| Percentage | a fraction out of 100. |
| x% | = x/100. |
| Of an amount | multiply by the fraction. |
| Fraction to percent | × 100. |
| Decimal to percent | × 100. |
| Change | change / original × 100. |
| Open the Virtual Lab |
These free Grade 8 Maths revision notes explain percentages as fractions, converting between forms and percentage change problems, with clear step by step worked examples and labelled diagrams for every student following the new Ganita Prakash book.
© 2026 School Revise. All rights reserved. This lesson is original content written by School Revise, aligned to the CBSE and NCERT Class 8 Mathematics (Ganita Prakash) syllabus. Unauthorised copying, reproduction or redistribution is not permitted. Curriculum names are used only to indicate alignment.
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