Mixing Two Solutions
Add up the solute from both, then divide by the combined mass. Averaging the two concentrations fails when the amounts differ.
Your numbers
Concentration
18%
Solution (g)
500g
Solute (g)
90g
Formula
Concentration = (A × A share + B × B share) ÷ (A + B)
200 g of 30% plus 300 g of 10% gives 18%, not the 20% you get by averaging.
What to enter
| Input | Default | Accepted range |
|---|---|---|
| A (g)The first number of the ratio — the 2 in 2:3. | 200 | 0 and up |
| A share (%)The percentage that applies to the first item. | 30 | 0 ~ 100 |
| B (g)The second number of the ratio — the 3 in 2:3. | 300 | 0 and up |
| B share (%)The percentage that applies to the second item. | 10 | 0 ~ 100 |
Step by step
Quick reference table
Results when only A (g) changes and everything else stays put.
| A (g) | Concentration (%) | Solution (g) (g) | Solute (g) (g) |
|---|---|---|---|
| 100 | 15 | 400 | 60 |
| 150 | 16.67 | 450 | 75 |
| 200 | 18 | 500 | 90 |
| 300 | 20 | 600 | 120 |
| 400 | 21.43 | 700 | 150 |
What each result means
| Result | At default values |
|---|---|
| Concentration (%)How much of the whole is solute. | 18 |
| Solution (g) (g)Solute and solvent together. | 500 |
| Solute (g) (g)The stuff being dissolved — sugar, salt and the like. | 90 |
Common mistakes
200 g of 30% plus 300 g of 10% gives 18%, not the 20% you get by averaging.
Glossary
- A
- The first number of the ratio — the 2 in 2:3.
- A share
- The percentage that applies to the first item.
- B
- The second number of the ratio — the 3 in 2:3.
- B share
- The percentage that applies to the second item.
- Concentration
- How much of the whole is solute.
- Solution (g)
- Solute and solvent together.
- Solute (g)
- The stuff being dissolved — sugar, salt and the like.
Frequently asked questions
Q. How is Mixing Two Solutions calculated?
Concentration = (A × A share + B × B share) ÷ (A + B) — Add up the solute from both, then divide by the combined mass. Averaging the two concentrations fails when the amounts differ.
Q. Can you walk through an example?
With A 200g, A share 30%, B 300g, B share 10%, the answer is Concentration 18%.
Q. What do I need to enter?
Enter A, A share, B, B share. The result recalculates as you type, and an empty box counts as zero.
Q. How much does the answer move if I change a number?
Changing only A (g) moves the answer to A (g) 100 → Concentration (%) 15 and A (g) 400 → Concentration (%) 21.43. The table below lays out five steps.
Q. How are the numbers rounded?
Money is shown to the nearest whole unit, percentages to one decimal place and everything else to two. What you see is rounded; the calculation itself carries the unrounded value forward.
Q. Anything to watch out for?
200 g of 30% plus 300 g of 10% gives 18%, not the 20% you get by averaging.
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