Permutations And Combinations Question 379
Question: Let $ A={x|x $ is prime number and $ x<30} $ . The number of different rational numbers whose numerator and denominator belong to A is
Options:
A) 90
B) 180
C) 91
D) 100
Correct Answer: C [c] We have $ A={2,3,5,7,11,13,17,19,23,29} $ A contains 10 elements. So numerator and denominator each can be chosen in 10 ways. So no. of rational numbers $ =10\times 10-10=90 $ (Out of these selections, 10 numbers are simply 1)
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Answer:
Solution:
BETA
