A number when increased by 25% becomes equal to another number, which is 20% less than a third number. What is the ratio of the first number to the third number?

Correct option is C

Given
First number increased by 25% = Second number
Second number = Third number decreased by 20%
Formula Used
Percentage Increase = Value $$\times (1 + \frac{Rate}{100})$$​​

Percentage Decrease = Value $$\times (1 - \frac{Rate}{100})$$​​
Solution
Let the third number be 100.
Second number = 100 - 20% of 100 = 80.
Let the first number be x.
​$$x \times (1 + \frac{25}{100}) = 80 \\x \times 1.25 = 80\\x = \frac{80}{1.25} = 64\\$$​​
Ratio of the first number to the third number = 64 : 100
Simplifying the ratio = 16 : 25
Final Answer 
So the correct answer is (c) 
Exam Hall Method: