cvsmech wrote:
p and q are different two-digit prime numbers with the same digits, but in reversed order. What is the value of the larger of p and q?
(1) p + q = 110
(2) p – q = 36
I couldn't understand the OE. Can anyone help?
Following is how I would approach this question:
"p and q are different two-digit prime numbers with the same digits, but in reversed order."
Since we are talking about prime numbers, the only digits to consider here are 1, 3, 7 and 9.
(1) p + q = 110
I need a sum of something more than 100. I get that if I add something from 10s with something from 90s. So a possible pair is 19 and 91 but 91 is not prime.
I also get something more than 100 is I add something from 30s with something from 70s. So a possible pair is 37 and 73.
There is no other combination that can give me something close to 100.
(You can also think of it as finding numbers equidistant from 55. So something from 30s and something from 70s can be equidistant from something from 50s)
(2) p – q = 36
The difference of the numbers is around 40. Something from 30s and something from 70s can have a difference of around 40. So 37 and 73 is the required pair. There is no other combination possible where the difference could be around 40.
Answer (D)
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