Q.

 Express the number 24 as the sum of two odd primes.



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a

24 is the sum of 2 and 22 

b

24 is the sum of 1 and 23

c

24 is  sum of 3 and 21

d

24 is  sum of 5 and 19  

answer is D.

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Detailed Solution

Concept: Before moving to the question we must know what is prime number and prime odd number. The number which is divisible only by 1 and itself is called the prime number.  Every prime number is an odd prime number except 2. Here we will use trial and ht method to solve this question is the best method to solve these types of questions.
Here taking the Case 1 - 24 is the sum of 1 and 23. This could not be possible because 1 is neither a prime number nor composite number
Here taking Case 2- 24 is the sum of 2 and 22.This could not be possible because 2 is not a prime number.
Here taking the Case 3 -24 is the sum of 3 and 21. This could not be possible because 21 is not a prime number.
Here taking Case 4 -24 is the sum of 4 and 20. We will not take this answer because 4 is an even number and composite number and 24 is not a prime number.
Here taking case 5-  24  is the sum of 5 and 19. We will not take this answer because 5 and 19 both are odd prime numbers.
So 24 s the sum of 5 and 19 Hence,  option 4 is the correct answer.  
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