Learn About Chloe!
Logic
Level
2
Chloe is a girl, who likes some numbers and don't like other numbers.
Chloe likes the number 5, but not the number 4.
She also likes the numbers 7, 10, 13, 14 and 15, but not 9, 12, 16, 18.
Would Chloe like 20 or 21?
Only 21
None of them
Only 20
Both of them
This section requires Javascript.
You are seeing this because something didn't load right. We suggest you, (a) try
refreshing the page, (b) enabling javascript if it is disabled on your browser and,
finally, (c)
loading the
non-javascript version of this page
. We're sorry about the hassle.
1 solution
Prime Factorisation is key to the answer.
When you prime factorise the numbers Chloe likes, all the factorised primes are different.
But when you prime factorise the numbers Chloe does not like, at least 2 of the factorised primes are the same.
For example, 10 = 2 x 5, but 12 = 2 x 2 x 3
(Of course, that means Chloe likes all prime numbers!)
So we come back to the question of 20 and 21. 20 = 2 x 2 x 5, whereas 21 = 3 x 7.
Chloe will not like 20, but will like 21.