Hello, Peacewanters007!

I couldn't find an Arithmetic solution.

I *had* to use Algebra . . . sorry.

A jug weighed 1.8 kg when 2/7 of it was filled with water

and weighed 2.85 kg when it was filled 5/7.

Find:

(a) Weight of jug when it was empty.

(b) What was mass of jug when it was completely filled?

Let = weight of the empty jug.

Let = weight of water when jug is completely filled.

Code:

* *
| |
| |
| |
| - - - | 1.8 kg
|:::::::|
| 2/7 W |
|:::::::|
*-------*
J

When the jug is full, the total weight is 1.8 kg.

Equation #1: .

Code:

* *
| |
| - - - |
|:::::::|
|:::::::| 2.85 kg
| 5/7 W |
|:::::::|
|:::::::|
*-------*
J

When the jug is full, the total weight is 2.95 kg.

Equation #2: .

Subtract [1] from [2]: . .

Hence: .

Substitute into [1]: .

(a) The empty jug weighed: .

(b) The filled jug weighed: .