When 21 is added to 30 % of a number, it gives the number itself. Find the number.


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Answer:

30

Step by Step Explanation:
  1. Let us assume the number to be x.
    30 % of x = x ×  
    30
    100
      =  
    30x
    100
     
  2. If we look at the question carefully, we will notice that the number(x) is equal to the sum of 21 and 30 % of x.
    So, it can be written as:
    x = 21 +  
    30x
    100
     
    ⇒ x =  
    21 × 100 + 30x
    100
     
    ⇒ x =  
    2100 + 30x
    100
     
    By cross multiplying both the sides
    100 x = 2100 + 30x
    ⇒ 100 x - 30x = 2100
    ⇒ 70x = 2100
    ⇒ x =  
    2100
    70
     
    ⇒ x = 30
  3. Therefore, the number is 30.

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