Percentage Increase or Decrease Using Multiplier
Percentage Increase or Decrease Using Multiplier
To calculate percentage increases and decreases, we use Percentage multipliers. Percentage multipliers allow us to calculate percentage increases and percentage decreases very quickly with one single multiplication.
To increase an amount by 15% we start with 100% of the amount, then add 15% of the amount to it. We now have 100% + 15% = 115% of the amount.
So, to increase an amount by 15% in one step. we multiply the amount by 115% or 1.15. The value 1.15 is called the multiplier.
To decrease an amount by 15%, we start with 100 of the amount, then subtract 15% of the amount from it. We now have 100% - 15% = 85% of the amount.
So, to decrease an amount by 15% in one step. we multiply the amount by 85% or 0.85. The value 0.85 is called the multiplier.
Illustration 1: Evaluate the following:
(a) Increase 312 kg by 22%, giving your answer to 3 significant figures.
(b) Decrease Rs183 by 7%.
Solution :
(a) To increase by 22%, we multiply by 100% + 22% = 122%, which is 1.22. Hence, 1.22 is the multiplier.
the new amount = 1.22
312 kg = 380.64 kg
381 kg
(b) To decrease by 7%, we multiply by 100% - 7% = 93%, which is 0.93.
the new amount = 0.93
Rs 183 = Rs 170.19 = Rs 170
Illustration 2: Find the multiplier corresponding to an increase of 25%?
Solution: To increase an amount by 25% we start with 100% of the amount, then add 25% of the amount to it. We now have 100% + 25% = 125% of the amount.
So, to increase an amount by 25% in one step. we multiply the amount by 125% or 1.25. The value 1.25 is called the multiplier.
Illustration 3: The school fee of Jack increased by 30%. His last year school fee was Rs 2500 per month. Find the amount which Jack has to pay this year every month?
Solution: Original school fee of Jack = Rs 2500
Increase in fee this year = 30 %
So, now he has to pay = 2500 X multiplier
To increase an amount by 30% we start with 100% of the amount, then add 30% of the amount to it. We now have 100% + 30% = 130% of the amount.
So, to increase an amount by 30% in one step. we multiply the amount by 130% or 1.30. The value 1.30 is called the multiplier.
the new amount = 1.30 X Rs 2500 = Rs. 3250
So, Jack has to pay Rs 3250 this year every month.
Find the multiplier corresponding to a decrease of 10% | |||
| Right Option : C | |||
| View Explanation | |||
A quantity decreased from 90 to 75. What percent decrease is this? | |||
| Right Option : C | |||
| View Explanation | |||
A price rose from $5 to $7. What percent increase is this? | |||
| Right Option : A | |||
| View Explanation | |||
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