Question
Quantitative Aptitude Question on Number Systems
How many numbers between 90 and 600 have exactly three factors?
A
170
B
48
C
5
D
None of these
Answer
5
Explanation
Solution
The correct option is (C): 5.
Only those numbers which are squares of prime numbers have exactly three factors.
Now, 92 < 90 < 102 and 242 < 600 < 252
Thus, five prime numbers (from 10 to 24) whose squares lie in the range described above are 11, 13, 17, 19 and 23.