If the number is a multiple of 8, it is divisible by 8. The multiples of 8 are: 8, 16, 24, 32, 40, 48, 56, 64, 72, 80, 88... etc.
If a number is very big, let's say 176, see if you can deduct 80 from it. For this, 176 can be deducted by 80 twice, which will give you a remainder of 16 (I.e. 176 - 80 - 80 = 16". If this remainder (i.e. 16) is divisible by 8, 176 is divisible by 8.
For even larger numbers, try deducting 800, or even 8000.
Let's say you're trying to see if 2464 is divisible by 8. In this case, 2464 can be deducted by 800 thrice (I.e. 2464 - 800 - 800 - 800 = 64), and 64 is its remainder. Since 64 is divisible by 8, 2464 is divisible by 8.
Recall : When given a normal or Symmetric distribution, the mean of the distribution is at the centre with 0.5 or 50% of the distribution to either side (right and left) of the distribution.
Hence, if the mean = 21 ; then the percentage of student body with atleast 21 years is the percentage to the left of the distribution, which is 50%.
