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‘Per cent’ means ‘out of one hundred’. Symbol % is used to denote per cent
Some examples to convert a per cent into a fraction, ratio or decimal and vice versa.
1.
(i) 50% = 0.50
(ii) 7% = 0.07
(iii) 90% = = 0.90
(iv) 1% = 0.01
2.
(i) 10% of 100 = 10
(ii) 20% of 500 = 100
(iii) 30% of 1000 = 300
3.
(i) 5 out of 25 = 20%
(ii) Re 1 out of Rs 25 = 4%
(iii) 10 out of 50 = 20%
Example 1.
(a) If 25% of X= 30. find X
Sol. 25% of X is and it is equal to 30
(b) If 24% of X is 48, then find X
Sol. 24% of X is 48
Example 2: Vijay deposits Rs 45 per month in the bank. If this amount is 15% of his monthly income, find his monthly income.
Solution: Let his monthly income be Rs X
As per the given statement 15% of X is 45
or x = = 300 RS
Example 3: Gunpowder contains 75% nitre and 10% sulphur. The rest of the material is charcoal. Find the amount of each of the contents in 9 kg of gunpowder.
Solution: Weight of gunpowder = 9 kg
Contents are – nitre = 75%, Sulphur = 10% charcoal = 1007510 = 15%
Nitre in 9 kg = = 6.75 kg
Sulphur in 9 kg = = 0.90 kg
Charcoal in 9 kg = = 1.35 kg
Example 4: Ankits salary is 25% more than that of Anil. What percent is Anil’s salary less than Ankits?
Solution: Let Anil’s salary be Rs 100
Then Ankit gets 25% more than Anil = 125
If Ankit’s salary is Rs 125 Anil’s = 100
If Ankit’s salary is Rs 100 then Anil’s =
So, Anils salary is Rs 80 when Ankit’s is Rs 100
So, Anil salary is 20% less than Ankit
Example 5: Raman loses 20% of his money. After spending 25% of the remaining, he has Rs 480. How much did he originally had?
Solution: Suppose Raman had Rs 100 in the beginning. He lost 20% i.e. Rs. 20
Remainder = Rs 100 – Rs 20 = Rs 80
Out of Rs 80 he spent 25%, which is equal to
Remainder = Rs 80 – Rs 20 = Rs 60
If remainder is Rs 60, he originally had = Rs 100
If remainder is Rs1, he originally had =
If remainder is Rs 480 he originally had =
Example 6: The price of a shirt in Dec 1997 was Rs 250. In Jan. 1998 it was increased by 10% and in Oct 1998 it was reduced by 10%. What in the new price of the shirt.
Solution: Price in Dec 1997 = Rs 250
Price in Jan 1998 =
Price in Oct 1998 = 275 x = Rs 247.50
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56 videos35 docs91 tests
