Can someone please explain how Greg got 4(10)^-8 and 2(10)^-4 for the numerator and denominator? Also which video concept series cover these types of problems? Any help much appreciated!

what he did was re-write the 15.99999996 to 16-4x10^-8 (because we need that 6 at the 8th position after the decimal) & re-write 4.0002 as 4 + 2x10^-4 so that we get 2 at the 4th position after the decimal

But why wouldn’t it be 16-8x10^-8? Where is the 4 coming from?

to get 6 at the end we need to do subtract it by 4 , if you do 16 - 8x10^-8 you will end up getting 2 as the last digit instead of 6

Ah okay! so it’s just a matter of subtraction? Is that how I should be looking at it?

Let do some examples :

If the question was 15.6 —> we would have done 16 - 4x10^-1 —>77/5 or 15.6

If the question was 15.96 ---->we would have done 16 - 4x10^-2 —>399/25 or15.96

If the question was 15.996 ---->we would have done 16 - 4x10^-3 —>3999/250 or15.996

Now the question is 15.99999996 —> so we did 16-4x10^-8 --> 15.99999996