All numbers divisible by 4 must also be divisible by 8 and all numbers divisible by 8 must also be divisible by 4
False
If a number is divisible by a number 'n', it is also divisible by the factors of 'n'.
Factors of 8 = 1, 2, 4, 8
Any number divisible by 8 will also be divisible by 4.
But vice-versa is not true. For example 20 is divisible by 4 but not divisible by 8