Hello, agus hendro!

Here's the first one . . .

Consider the number of kgs of water at each stage.1. 1000 kgs of chemical is stored in a container.

The chemical is made up of 99% water and 1% oil.

Some water is evaporated until the water content is reduced to 96%.

How much does the chemical weigh now?

We start with 1000 kgs of solution which is 99% water.

. . It contains: . kgs of water.

We remove kgs of water.

. . It now contains: . kgs of water.

Start again . . . We have 1000 kgs of solution.

. . We remove kgs of water.

So we have: kgs of stuff.

But this is supposed to be 96% water.

. . So it contains: . kgs of water.

We just described the final amount of water intwoways.

There is our equation! . . . .