35 ml of a sample are obtained from a crime scene where the ratio of blood to water is 7:3. how much of the sample was blood?

Answer 1

let the amount of blood be 7x
the amount of water be 3x

7x + 3x = 35
x = 3.5

then 7x = 24.5

24.5 ml was blood, and 10.5 was water

check:
24.5 : 10.5
= 49 : 21
= 7 : 3