Co n c e p t By t e U n i t A n a l y s i s
Use W ith Lesson 2-6Common Core State Standards
N-Q.A.1 Use units as a way to understand problems
and to guide the solution o f multi-step problems; choose
and interpret units consistently in formulas.
MP 6In Lesson 2-6, you learn ed th a t you can use u n it analysis w h en converting units. You
can also use u n it analysis to help guide you to th e solution of a problem.Activity 1
The speed of light is about 3.0 x 10 10 cm /s. If a rocket car of the future can travel at
the speed of light, what is this rate in miles per hour?Step 1 Make sense of the given information.- W hat units are given in th e problem statem ent?
- W hat u n its of m easure should you have in your answer?
Step 2 Formulate a plan to solve the problem. - W hat units n e e d to be converted to solve th e problem?
- How do you know w hich conversion factors to use to solve th e problem?
- Can you use different conversion factors to solve th e problem? Explain.
Step 3 Solve the problem.
6. Use u n it analysis to write an expression by using th e conversion factors
you chose in Step 2.- Simplify the expression.
Step 4 Check your solution. - Are th e u nits of your solution w hat you expected? Explain.
- Does your answer make sense? Explain.
Ife S lMATHEMAtlCAL
PRACTICESYou can also use unit analysis to determ ine th e reasonableness of a solution or a claim.Activity 2
Suppose you are a gold miner in California in 1849. You have your tools in one
hand. Can you use your free hand to carry a 4-liter bucket full of gold dust? The
density of gold is 19.3 g/cm 3. Use unit analysis to determine whether the bucket is
too heavy to carry. (Hint: 1 lb » 454 g and 1000 cm 3 = 1 L.)
Step 1 Make sense of the given information.- W hat units are given in the p roblem statem ent?
- D escribe w hat you n e e d to find in o rder to d eterm in e w h e th e r the
bucket is too heavy to carry.
122 Chapter 2 Solving Equations