If example says, there are total 1600 people. from total, man is 15% more than women... how to find number of man and women from 1600?
What I did is:
- 100 - 15 = 85
- Divide 85/2 = 42.5
- 42.5% of 1600 = 680
- 680 + 680 = 1360. 1600 - 1360 = 240
- Man = 680 + 240 = 920
- Women = 680
I know there can be better way, can someone help me?
You'd get it easier using a system of equations.
Making the most of the chromosome distinction, let $x$ be the numebr of women and $y$ the numebr of men.
The total people is 1600: $x+y=1600$
And men are 15% more than women, that is, $y=1,15 \cdot x$ (because 15% more = 100% + 15% = 115% = 115/100).
Consequently, if you replace above, you'll have
$x+1,15 x = 1600 \Rightarrow 2,15x=1600 \ \Rightarrow \ x= \frac{1600}{2,15}=744,18$
This is obviously impossible, which makes me think I've misunderstood your question. Re-reading it, I could have also understood that "15% of the total is the difference between men and women", (being more men), but it should have been clearer.
In that case, you write
$0,15\cdot 1600 = y-x$
and that's your second equation. By the way, 15% of 1600 is 240.
So your both equations are $x+y=1600$ and $y-x=240$.
This is a very easy system whose solution is $y=920$ men and $x=680$ women.