Unit B: Measurement

Practice


Instructions: Click the Download File button to download a printable PDF of the questions. Answer each of the following practice questions on a separate piece of paper. Step by step solutions are provided under the Solutions tab. You will learn the material more thoroughly if you complete the questions before checking the answers.
Download File


Zara has 50 cm of ribbon to tie fabric to the jars of preserves she sells at the local farmer's market. To tie each jar, she uses 10 cm of ribbon.

  1. State the precision and uncertainty of each measurement.
  2. After cutting one piece of ribbon, how much ribbon does Zara have left?
  3. Zara expects to have enough ribbon to tie five jars. When she attempts to tie the fifth ribbon, she discovers it measures only 8 cm. Why?
Zara has 50 cm of ribbon to tie fabric to the jars of preserves she sells at the local farmer's market. To tie each jar, she uses 10 cm of ribbon.

  1. State the precision and uncertainty of each measurement.
  2. After cutting one piece of ribbon, how much ribbon does Zara have left?
  3. Zara expects to have enough ribbon to tie five jars. When she attempts to tie the fifth ribbon, she discovers it measures only 8 cm. Why?

  1. Both the original ribbon and each cut ribbon have a precision of 1 cm and an uncertainty of 0.05 cm.
    Original ribbon: 50 cm ± 0.5 cm
    Cut ribbon: 10 cm ± 0.5 cm

  2. First calculate the measured amount of ribbon left.
    50 cm – 10 cm = 40 cm
    Next, calculate the uncertainty of the ribbon left.
    0.5 cm + 0.5 cm = 1.0 cm
    Therefore, the ribbon left is 40 cm ± 1.0 cm.

  3. After cutting four pieces of ribbon, Zara is left with
    50 cm – 10 cm – 10 cm – 10 cm – 10 cm = 10 cm
    and an uncertainty of
    0.5 cm + 0.5 cm + 0.5 cm + 0.5 cm + 0.5 cm = 2.5 cm
    Therefore, before using the last piece, Zara is left with 10 cm ± 2.5 cm.
    This means that she could have between 7.5 cm and 12.5 cm of ribbon left.