Let’s take an Example

54 is a 2 digit number.

 

Digits at ten places = 5

Digit at units place = 4

 

So, the number will be

Number = (10 × Digits at ten place) + (1 × Digit at units place)

        = (10 ×  5) + (1 ×  4)

        = 50 + 4

        = 54

 

To generalize

Number

Digits are interchanged

Let number be

    ab

 

So, Digit at tens place = a

  & Digit at unit place = b

 

Number

  = (10 × Digit at tens place)  
      +  (1 × Digit at units place)

     = (10 × a) + (1 × b)

= 10a + b

Thus, number will be

    ba

 

So, Digit at tens place = b

  & Digit at unit place = a

 

Number

  = (10 × Digit at tens place)  
      +  (1 × Digit at units place)

     = (10 × b) + (1 × a)

= 10b + a

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Davneet Singh

Davneet Singh has done his B.Tech from Indian Institute of Technology, Kanpur. He has been teaching from the past 13 years. He provides courses for Maths, Science, Social Science, Physics, Chemistry, Computer Science at Teachoo.