Problem Solving WS 4 Formulas
Name _________________ Per. ___
Solve each of the following problems by using a formula. Show all your work.
1. The formula for calculating the simple interest on a loan is principal x rate x years. If Mr. Rogers
had a loan with a principal of $288 and a 6% interest rate, how much would he pay in interest after
half a year?
1
2. The formula for the area of a trapezoid is 2 (𝑏1 + 𝑏2 ) ∙ ℎ where h represents the height, b1
represents the length of one of the parallel sides, and b2 represents the length of the other parallel
side. Find the area of the trapezoid below.
3. Use a formula to find the volume of a sphere with a diameter of 10 cm. Yes, you have to get on
the internet to find the formula yourself. 
Class Problems
1. To change Fahrenheit degrees to Celsius, you subtract 32, multiply by 5, and divide by 9.
The formula is as follows where C = degrees in Celsius and F = degrees in Fahrenheit.
5
𝐶 = (𝐹 − 32)
9
a. If it is 90 degrees Fahrenheit outside, what is the temperature in Celsius?
b. If it is 20 degrees Celsius, what is the temperature in Fahrenheit? Ah ha!
2. A triangle has 180 degrees. A quadrilateral has 360 degrees.
a. Using this pattern, find out how many degrees an octagon has.
b. Use this pattern to write a formula that helps you find the degrees in a polygon given the
number of sides.
c. Use your formula to calculate the number of degrees in a 50-sided figure.