# How much gram of sorbitol, should I to weigh on the balance?

1. Jan 30, 2016

### Cyrus the great

1. The problem statement, all variables and given/known data
I have 4.6 gram of starch and I want to add 30 % of sorbitol to xylan. How much gram of sorbitol, should I weigh on the balance?

2. Relevant equations

3. The attempt at a solution

2. Jan 30, 2016

### Dr. Courtney

It is not clear whether you are talking about xylan as your starch, or whether it is in addition to the starch and sorbitol.

It is also unclear whether you want to add 30% of the existing amount or whether you want sorbitol to be 30% of the total amount.

3. Jan 30, 2016

### Cyrus the great

yes I meant xylan as my starch and I want sorbitol to be 30% of the total amount.

4. Jan 30, 2016

### Dr. Courtney

Let x be the amount of sorbitol to add, in grams.

Let T be total amount.

x = 0.3*T

But you can also express the total amount T in terms of x and the initial amount of starch.

Do that, substitute into the above equation, solve for x.

Double check that x is 30% of T.

5. Jan 30, 2016

### Cyrus the great

I want to add 30 % sorbitol to my starch. Therefore, I calculated like below.
starch starch
70 100
4.6 X

X=4.6*100/70= 6.50 g. So, amount of sorbitol needed is 6.5-4.6=1.96 g

But If I do like your way X=4.6 * 0.3=1.38 gram

Now I have got confused. Which number is correct?

6. Jan 31, 2016

### Cyrus the great

I want sorbitol to be 30% of the total amount. So if I have 70 % starch I have 4.6 g and if I want to have 100 % then how much starch it would be which becomes 6.5.

X=4.6*100/70= 6.57

Then I deducted 6.5 from 4.6 which it becomes 6.5-4.6=1.97 gram of sorbitol should be added to the starch.

Is my calculation correct?

Last edited: Jan 31, 2016