Question

What is $50\% $ of a number whose $200\% $ is $20$?
A.$5$
B.$10$
C.$15$
D.$20$

Answer 1

Hint:Firstly, we need to find out the number with the data given to us. Then after we are able to find out percent of that number easily. We can find out the answer without finding the number also. The way is to multiply the percentage given with suitable value to get the percentage asked. Then you must multiply the value with the same number to get the solution.


Complete step-by-step answer:
Given that $200\% $ of a number is $20$.
We are asked to find out the value of $50\% $ of the same number.
Let us assume that unknown number to be $x$.
Now, calculate the $200\% $ of the number.
It can be calculated as follows:
$200\% $ of the number $ = \dfrac{{200}}{{100}} \times x$
            $ = 2x$
But as per the data $200\% $ of the number is $20$.
Equate the both values to get the value of $x$
$
   \Rightarrow 2x = 20 \\
   \Rightarrow x = 10 \\
 $
So, we got the value of the number.
But we are not asked to find out the value of the number. We are asked to find out the value of $50\% $ of that number.
$50\% $ of $10$ $ = \dfrac{{50}}{{100}} \times 10$
$
   = \dfrac{1}{2} \times 10 \\
   = 5 \\
 $
So, we got the solution as $5$.
Hence $50\% $ of the number is $5$.

So, the correct answer is “Option A”.

Note:We need to compare the percentage given with the percentage asked and multiply the percentage given with suitable value to get the percentage asked. Now, you need to multiply the given value with the same number to get the asked value. This makes your calculation faster and at the same time you can save your time.