Problem 322
You know that a number us divisible by 6 if it is divisible by both 3 and 2. So why isn’t number divisible by 8 if it is divisible by both 4 and 2 ?
Solution
If the a number is divisible by some prime numbers it means that number is also divisible by the multiple of those prime numbers, so in first case both factors are prime , but in second care factors are not prime so there is no any surety that the number will be divisible by 8.