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If 20% of a number is 80, what is 50% of the same number?
200
250
150
300
200
Use the unitary method: since 20% is 80, 10% is 40. Therefore, 50% is 40├Ч5=200.
20% of a number is 80.
x=PercentageValueтАЛ├Ч100
Use the unitary method: since 20% is 80, 10% is 40. Therefore, 50% is 40├Ч5=200.
Students often calculate the number itself first (which is 400) and then calculate 50% of it, which wastes time compared to using the ratio of percentages.
Define the relationship
Let the number be x. We are given that 20% of x equals 80.
0.20x=80
Calculate the target percentage
We need to find 50% of x. We can express 50% as 2.5├Ч20%.
50%=2.5├Ч20%
Final calculation
Multiply the given value 80 by 2.5 to get the result.
80├Ч2.5=200
A is correct because 50% of the number is calculated as (80├╖20)├Ч50=200.
This ratio-based approach is extremely useful in Data Interpretation (DI) sets where you need to quickly estimate proportions without finding the exact base value.