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I don't think this answer, while it gets you to the same result, follows the right logic.

Why is 19 not included in Set B? It is also a prime number under 20

Also, 25n when n=3 and 15n when n=5 produce the same value, and the question is asking for distinct numbers!

So you are missing one and duplicating another one, hence why you get to the right answer, but incorrect logic?
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Set X= {5,10,15,20.....}
Set Y= {3,5,7,11,13,17,19)

Set Z = product of one element from set X and one element from set Y < 100 (Distinct integers)

From Set Y '3' can get multiplied upto '30' from Set X, so that product is < 100. All values {15,30,45,60,75,90}= 6 values
From Set Y '5' can get multiplied upto '15' from Set X, so that product is < 100. All values {25,50,75}= 3 values
From Set Y '7' can get multiplied to '10' from Set X, so that product is < 100. All values {35,70}= 2 values
From Set Y '11' can get multiplied to only '5' from Set X, so that product is < 100. Only value is {55}= 1 value
From Set Y '13' can get multiplied to only '5' from Set X, so that product is < 100. Only value is {65}= 1 value
From Set Y '17' can get multiplied to only '5' from Set X, so that product is < 100. Only value is {85}= 1 value
From Set Y '19' can get multiplied to only '5' from Set X, so that product is < 100. Only value is {95}= 1 value

Total values : 6+3+2+1+1+1+1 = 15.

The common value is 1 which is {75} for both '3' and '5' and we need the distinct integers.

Hence Set Z has total 15-1 = 14 elements.

Answer : B
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