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KVPY 2019 SA Exam Previous Papers
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© examsnet.com
Question : 10
Total: 80
A two-digit number
–
–
–
a
b
is called almost prime if one obtains a two-digit prime number by changing at most one of its digits a and b. (For example, 18 is an almost prime number because 13 is a prime number).
Then the number of almost prime two-digit numbers is :
56
75
87
90
Validate
Solution:
Since there exists a prime in every set of the form {10a + b, a = 1, 2, ….,9, b = 0, 1, 2,….,9}
Hence every two digit number is almost prime.
© examsnet.com
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