Lesson 7
Changing Elevation
Let's solve problems about adding signed numbers.
Problem 1
What is the final elevation if
 A bird starts at 20 m and changes 16 m?
 A butterfly starts at 20 m and changes 16 m?
 A diver starts at 5 m and changes 16 m?
 A whale starts at 9 m and changes 11 m?
 A fish starts at 9 meters and changes 11 meters?
Problem 2
One of the particles in an atom is called an electron. It has a charge of 1. Another particle in an atom is a proton. It has charge of +1. The charge of an atom is the sum of the charges of the electrons and the protons. A carbon atom has an overall charge of 0, because it has 6 electrons and 6 protons and \(\text 6 + 6 = 0\). Find the overall charge for the rest of the elements on the list.
charge from electrons 
charge from protons 
overall charge 


carbon  6  +6  0 
neon  10  +10  
oxide  10  +8  
copper  27  +29  
tin  50  +50 
Problem 3
Add.
\(14.7 +28.9\)
\(\text9.2 + 4.4\)
\(\text81.4 + (\text12)\)
\(51.8 + (\text0.8)\)
Problem 4
Select all the true statements.
\(\text5 < \text5\)
\(\text6 < \text5\)
\(\text6 < 3\)
\(4 < \text7\)
\(\text7 < \text8\)
Problem 5
Last week, the price, in dollars, of a gallon of gasoline was \(g\). This week, the price of gasoline per gallon increased by 5%. Which expressions represent this week's price, in dollars, of a gallon of gasoline? Select all that apply.
\(g + 0.05\)
\(g + 0.05g\)
\(1.05g\)
\(0.05g\)
\((1+0.05)g\)
Problem 6
A family goes to a restaurant. When the bill comes, this is printed at the bottom of it:
Gratuity Guide For Your Convenience: 15% would be $4.89 18% would be $5.87 20% would be $6.52 
How much was the price of the meal? Explain your reasoning.