Question

Two times a number is a 100% increase in the number. If we take half
the number what would be the decrease in per cent?
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Answer 1

50%.................. ......

Answer 2

$\huge\sf\red{answer}$

Let the number be x and half the number is

$\frac{x}{2}$

Now, decrease in the number

$= x - \frac{x}{2} = \frac{2x - x}{2} = \frac{x}{2}$

Hence, decrease percent

$= ( 100 \times \frac{decrease}{original \: value} )\% \\ = (100 \times \frac{x \div 100}{x}) \% \\ = (100 \times \frac{x}{2 \times x} )\% \\ = 50\%$