# Tutor profile: Michael C.

## Questions

### Subject: Pre-Algebra

Solve the following expression: 4 times 2^3 - (6- 3). (Note: the ^ symbol represents an exponent)

Let's work this out. We need to remember PEMDAS. The original is: 4 times 2^3 - (6 - 3). The first step is to simplify the parenthesis. 6 - 3 = 3 4 times 2^3 - 3. Next step is the exponent. 2^3 = 8. 4 times 8 - 3. Now we look for any multiplication or division. 4 times 8 = 32. 32 - 3. And then finish off with subtraction. 29.

### Subject: Chemistry

What is percent carbon in glucose?

In order to solve this question we need a few things: chemical formula of glucose and a periodic table. The chemical formula of glucose is C6H12O6. That means this molecule has 6 carbon atoms, 12 hydrogen atoms, and 6 oxygen atoms. Now we must calculate the mass of the sum of the carbon atoms, and divide that number by the mass of the entire glucose molecule! The mass of 1 carbon atom is 12.011 amu (refer to periodic table to get this number). Since there are 6 carbon atoms in glucose, the total sum of all carbon atoms is 6 times 12.011 = 72.066. Now, to calculate the mass of the glucose molecule, we apply the same logic: we do (6 times 12.011) + (12 times 1.008) + (6 times 15.999) = 180.156 amu. Now we divide the mass of the carbon atoms over the mass of the entire molecule: 72.066 divided by 180.156 = 0.4000. Multiply this by 100 to give us the answer in percentage: 40.00%. Therefore, the percent carbon in glucose is 40%!

### Subject: Algebra

The price of toilet paper has increase from $5 to $8. By how many percent did the price increase?

-Logically, this question is asking, "The price increase in $ is what % of the original price?" Written out on paper, it would look like: Price increase ($) = x % times original price ($). -So we need to determine a) "the price increase in $ and b) the "original price". Then we can solve! -Determine "the price increase in $": The price increase from $5 to $8. $8 - $5 = $3. Therefore the price increase in $ = $3. -Determine the "original price": the original price is $5 (this was given to us!) -Solve (using formula above): $3 = x % times $5. Solving for x, we get $3 / $5 = 0.6. Multiply by 100 to convert to a percentage, which gives us 60%. -Final answer: the price increased by 60%.

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