Section B Section B Checkpoint

Problem 1

Find each product or quotient.
  1. -4⋅10\text-4 \boldcdot 10
  2. -5⋅-11\text-5 \boldcdot \text-11
  3. (3.6)⋅ (-0.2)(3.6) \boldcdot  (\text-0.2)
  4. -20÷-4\text-20 \div \text-4
  5. 34÷(-13)\frac34 \div \left( \text-\frac13 \right)
Show Solution
Solution
  1. -40
  2. 55
  3. -0.72
  4. 5
  5. -94\text-\frac94 (or equivalent)
Show Sample Response
Sample Response
  1. -40
  2. 55
  3. -0.72
  4. 5
  5. -94\text-\frac94 (or equivalent)

Problem 2

One train is traveling north at 10 meters per second. On a parallel track, another train is traveling south at 7 meters per second.

  1. How could we use signed numbers to represent this situation?
  2. Where was each train engine 5 seconds before they passed each other?
Show Solution
Solution
  1. Sample response: We could use positive numbers to represent movement to the north and negative numbers to represent movement to the south.
  2. The first train was 50 meters south of the crossing point, because 10⋅-5=-5010 \boldcdot \text-5 = \text-50. The second train was 35 meters north of the crossing point, because -7⋅-5=35\text-7 \boldcdot \text-5 = 35.
Show Sample Response
Sample Response
  1. Sample response: We could use positive numbers to represent movement to the north and negative numbers to represent movement to the south.
  2. The first train was 50 meters south of the crossing point, because 10⋅-5=-5010 \boldcdot \text-5 = \text-50. The second train was 35 meters north of the crossing point, because -7⋅-5=35\text-7 \boldcdot \text-5 = 35.