If in 100 liters of water 1mL drop of solution equals to 1 ppm

Question

For a starter im an information system college student, im working on a prototype for my final test about liquid dosing for plant. Here is the question :

If in 100 Liters of water in a tank 1 mL drop of solution equals to 1 ppm,

in 10 liters 1 mL drop equals to 10 ppm,

and in 1 liter 1 mL drop equals to 100 ppm.

Is this sounds right? if it do, how many ppm do i get for 1 mL drop in 7 liters of water in a tank?

Answer 1

1 L = 1000 mL

100 L = 100000 mL

1000 L = 1,000,000 mL

1 mL / 1000 L = 1 ppm

1 mL : 7 L :: x : 1,000,000

1 mL : 7000 mL :: x : 1,000,000

7000 x = 1,000,000

x = 142.857

1 mL is 142.857 ppm in 7 L