Iron ore contains 7.8% iron, find the mass of iron at 3 tons of ore.

Let’s apply a percentage.

Let 3 tons of ore contain 100% iron, then x tons contain 7.8% iron.

Hence:

3 t – 100%,

x t – 7.8%.

Therefore: x t * 100% = 3 t * 7.8%.

x = 3 * 7.8% / 100% = 0.234 tons.

Let’s translate the result into kilograms, since 1 t = 1000 kg, then: 0.234 t = 0.234 t * 1000 kg = 234 kg.

Answer: 3 tons of ore contains 234 kilograms of iron.