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the number of two digit prime number s which remain prime even on inverting the position of its digit is:
i ve attempted ans 3 then too i ve not how it's is 9 so pls explain me it in full detail
Answers (1)
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Total numbers of two digit prime numbers are.
Now, from above we can only take.
11,13,17,19,31,37,71,73,49,97&leave the rest ones .
Because if we reverse these digits then,
23 - 32 (divisible by 2,4,___ )
29 - 92 (divisible by 2,4,___ )
41 - 14
43 - 34
47 - 74 & so on.
, In total there are 10 prime numbers are 11(
, both the digits are same)
So, we can say entirely there are only a digits. excepting 11.