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

What is the formula for density?

DensityDensity = = MassMass / / VolumeVolume

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 solidssolids and gasesgases.

• 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 equationadd 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.

First, here’s what the triangle will look like:

Copy it down along with the 4 steps to solving.

x÷ ÷

1. Write down what you know and don’t know in the problem

2. Cover-up the variable that you’re trying to find. Read what the triangle says to do. Write down the formula.

3. Plug-in the numbers for the variables and solve

4. Make sure to have units on your answers.

MassMass

DensityDensity VolumeVolume

Example 1Example 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 = 907.1 g

• AssignmentAssignment: • “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.