Consider the following statements :

1. log10 50 is a rational number.

2. log100 10 is an irrational number.

Which of the statements given above is/are correct ?

This question was previously asked in
CDS Elementary Mathematics 16 April 2023 Official Paper
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  1. 1 only  
  2. 2 only  
  3. Both 1 and 2 
  4. Neither 1 nor 2

Answer (Detailed Solution Below)

Option 4 : Neither 1 nor 2
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Detailed Solution

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Concept:

  • For any base b which is a transcendental number the logarithm logbn of every integer n ≥ 2 is an irrational number.
  • A rational number is a number, which can be written as p/q where p & q are integers and q ≠ 0. 

Formula used:

  • log mn = log m + log n 
  • logaa = 1
  • loganb = (1/n) logab

 

Calculation:

Statement:1 log1050 is a rational number.

log1050 = log1050 =  log10(5 × 10)

log1050 = log105 + log1010   

log1050 = log105 + 1

As discussed, log105 is an irrational number, log1050 will be also irrational.

Statement:2  log100 10 is an irrational number.

log10010 = log10210 = (1/2)log1010 = 1/2

Which is a rational number.

∴ Both statements are incorrect.

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