How many cups is 34 doubled

A liquid with pH 3 contains twice as many H + ions as one with pH 4. Is this statement true or false?

I am from same volume assumed for both solutions and, for the sake of simplicity, from 1 liter.

1 liter of the solution with pH 4 contains 10⁻⁴ or 0.0001 mol H⁺.

1 liter of the solution with pH 3 contains 10⁻³ or 0.001 mol H⁺.

This makes the statement wrong, because the pH 3 solution contains 10 times as many mol H⁺ as the pH 4 solution.

With this approach you don't need to calculate, just compare the values.

But there is how Tom Richter has already written another possible solution if one of different volumes goes out.

In 1 liter the solution with pH 4 are 0.0001 mol H⁺ contain.

In 1 liter the solution with pH 3 are 0.001 mol H⁺ contain. But:

In 0.2 liters the solution with pH 3 are just left 0.0002 mol H⁺ contain.

Given this assumption of different volumes, the statement is correct:

0.2 liters the solution with pH 3 contain twice as many H⁺ as 1 liter the solution with pH 4.