Ratios & Percentages

Chapter 7 Class 8 Comparing Quantities
Concept wise

Let’s say,

Harshit has scored following marks in  5 subjects
(out of 100):80, 75, 95, 70, 80 and we have to calculate
his percentage

Marks scored = 80 + 75 + 95 + 70 + 80

= 155 + 165 + 80

= 320 + 80

= 400

Total marks = 100 + 100 + 100 + 100 + 100

= 500

Percentage marks = (Marks scored)/(Total marks) × 100%

= 400/500 × 100%

= 4/5 × 100%

= 4 × 20%

= 80%

#### Let’s assume another situation,

A milkman mixes 5 l   water in 45 l of milk before distributing it. What percentage of water is there in distributed milk?

Amount of water = 5 l

Total amount of milk = Amount of milk + Amount of water

= 45 l + 5 l

= 50 l

Percentage of water added = (Amount of water)/(Total amount of milk) × 100%

= 5/50 × 100%

= 1/10 × 100%

= 10%

#### Madhu bought a dress worth Rs 1,000 in Rs 800 after bar-gaining with shopkeeper. What percentage of discount did she managed to get?

Actual price = Rs 1000

Discount = 1000 − 800

= Rs 200

Percentage of discount = Discount/Amount × 100%

= 200/1000 × 100%

= 2/10 × 100%

= 1/5 × 100%

= 20%