07: Percent And Percentage Class 8 Maths : Icse-viii-mathematics

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ICSE-VIII-Mathematics

07: Percent and Percentage Class 8 Maths

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Section : A

Qstn #1
Evaluate:

#1-i
55% of 160 + 24% of 50 - 36% of 150
Ans : 55% of 160 + 24% of 50 - 36% of 150
= (55 × 160)/100 + (24 × 50)/100 - (36 × 150)/100
= 11 × 8 + 12 - 18 × 3 = 88 + 12 - 54 = 46

#1-ii
9.3% of 500 - 4.8% of 250 - 2.5% of 240
Ans : 9.3 % of 500 - 4.8% of 250 - 2.5% of 240
= (9.3 × 500)/100 - (4.8 × 250)/100 - (2.5 × 240)/100
9.3 × 5 - 1.2 × 10 - 0.5 × 12
= 46.5 - 12 - 6
= 46. 5 - 8
= 28.5

#2

#2-i
A number is increased from 125 to 150; find the percentage increase.
Ans : Original value = 125, New value = 150
Increase = (150 - 125) = 25
Increase % = 25/125 × 100 = 20%

#2-ii
A number is decreased from 125 to 100; find the percentage decrease.
Ans : Original number = 125, New value = 100,
Decrease = (125 - 100) = 25
Decrease % = 25/125 × 100 = 200%

Qstn #3
Find:

#3-i
45 is what percent of 54?
Ans : Let 45 = x percent of 54 = (54 × x)/100
⇒ x = (45 × 100)/54 = (5 × 100)/6
= 250/3 = 83 1/3%
∴ Reqd. percentage = 83 1/3%

#3-ii
2.7 is what percent of 18?
Ans : Let 2.7 = x percent of 18 = (18 × x)/100
∴ x = (2.7 × 100)/18 = 270/18 = 30/2 = 15
∴ Reqd. percentage = 15%

#4

#4-i
252 is 35% of a certain number, find the number.
Ans : Let the number be x
By the given condition,
252 = (x × 35)/100 = (x × 7)/20
∴ x = (252 × 20)/7 = 36 × 20 = 720
Hence reqd. number = 720

#4-ii
If 14% of a number is 315; find the number.
Ans : Let the number be x
By the given condition,
315 = (x × 14)/100
∴ x = (315 × 100)/14
= (45 × 100)/2
= 45 × 50
= 2250
Hence, reqd. number = 2250

Qstn #5
Find the percentage change, when a number is changed from :