1. Density Calculation
Students will be able to use the “Magic Triangle” to solve density problems.

2. g/cm3 are for solids and gases.
What is the formula for density?
Density = Mass / Volume
When doing these problems, your answers will have the same units as those that were used in the problem.
g/ml are for liquids
g/cm3 are for solids and gases.

3. Look at the following example: 4x – 6 = 10
How many of you can solve for an unknown variable in a formula?
Look at the following example:
4x – 6 = 10
First, you’d need to get all the numbers on one side of the “=“
Using your orders of operation, add 6 to both sides of the equation.
4x – 6 (+6)= 10+6
4x = 16
Divide by 4 on both sides
x = 4
Now not all of you can do this, so the “Magic Triangle” will help and it’s a tool for anyone to use.

4. ÷ ÷ x First, here’s what the triangle will look like:
Copy it down along with the 4 steps to solving.
1. Write down what you know and don’t know in the problem
Mass
2. Cover-up the variable that you’re trying to find. Read what the triangle says to do. Write down the formula. ÷ ÷ x
Density
Volume
3. Plug-in the numbers for the variables and solve
4. Make sure to have units on your answers.

5. Example 1
What is the mass of 47 cm3 piece of gold that has a density of 19.3 g/cm3 ?
Step 1: Write what you know and don’t know?
m= ? V= 47 cm3 D= 19.3 g/cm3
Step 2: Use the triangle and cover-up the ‘m’ and write down the formula that is shown.
m = D x v
Step 3: Plug-in the numbers and solve.
m = (19.3 g/cm3 ) x (47 cm3 )
m = g

6. Assignment:
“Density Practice Problems W.S.”
Problems 1 - 9
Do your calculations on another piece of paper and make sure to show your work like in example 1
Due by Friday.
You can use calculators to help you on the math.