Lesson 2

In Try This 4 you saw the following rules:

• You can add measurements with uncertainties by adding the measures and adding the uncertainties.
• You can subtract measurements with uncertainties by subtracting the measures and adding the uncertainties.

Notice that when you subtracted the measures with uncertainties, you still added the uncertainties.

Self-Check 2

1. Apply the rules of adding and subtracting measurements to the following.
   1. (22 ± 0.5 L) + (14 ± 0.5 L) Answer
   2. (17.5 ± 0.5 m) − (4.5 ± 0.5 m) Answer
   3. (28.2 ± 0.05 kg) + (17.4 ± 0.05 kg) Answer
   4. (34 ± 0.5 cm) − (19 ± 0.5 cm) Answer

2. 

   Hemera/Thinkstock

   An oilfield hotshot service delivers parts to oilfield rigs and plants in short notice situations. Jim’s Hotshot Service has a one-ton truck with a bumper pull trailer that is used to deliver the parts. Due to cold winter weather and the short notice of work, he plans to build a heated shop that will measure (40.0 ± 0.05) ft to store his truck and trailer in. Jim’s truck measures (21.6 ± 0.05) ft and his trailer measures (18.0 ± 0.05) ft.
   1. When hooked together, determine the maximum and minimum length of the truck and trailer. Answer
   2. How much space is needed for the truck and trailer to fit? Answer
   3. If they fit, how much additional space is left in the shop? Answer

You have learned that there are many practical applications that involve minimum and maximum measurements, such as the installation of flooring and determining what can fit in a shop. The ability to calculate the uncertainty in measurements helps to determine whether things can fit together and what the range of measurements could be.