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Numbers and operations · Ages 12–13

Using directed numbers worksheet

Part of: Directed numbers

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Using directed numbers worksheet

Numbers and operations · Ages 12–13

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Name:Date:Score:/48

Write each answer in the space. For word problems, show your working and write a sentence answer.

Part A: Working out and filling in (2 marks each)

  1. 1.It was −11°C at dawn and 15°C at noon. By how much did the temperature rise?

    Answer:

  2. 2.It is −13°C now. What is the temperature after it rises 16°C?

    Answer:

  3. 3.It is −12°C now. What is the temperature after it rises 8°C?

    Answer:

  4. 4.A shop's record over three days is +$750, −$500, −$150. With profit positive, what is its total over the three days, in dollars?

    Answer:

  5. 5.An account holds $400, and $700 is taken out (it may go overdrawn, written as negative). What is the balance, in dollars?

    Answer:

  6. 6.A shop's record over three days is +$300, −$350, −$150. With profit positive, what is its total over the three days, in dollars?

    Answer:

  7. 7.With London as 0, city A is −3 hours and city B +3 hours. How many hours is B's clock ahead of A's?

    Answer:

  8. 8.A quiz has 22 questions: +1 for right, −1 for wrong. All are answered, 17 wrong. What is the total score?

    Answer:

  9. 9.A quiz has 29 questions: +1 for right, −1 for wrong. All are answered, 6 wrong. What is the total score?

    Answer:

  10. 10.With London as 0, city A is −1 hours and city B +4 hours. How many hours is B's clock ahead of A's?

    Answer:

Part B: Choose, or true or false (2 marks each)

  1. 11.A submarine is 80 m below sea level and dives 50 m more. Which sum gives its new position?

    • A. (−80) + (−50)
    • B. (−80) + 50
    • C. 80 + (−50)
    • D. 80 − (−50)

    Choose the right answer

    Answer:

  2. 12.A submarine is 50 m below sea level and dives 70 m more. Which sum gives its new position?

    • A. 50 + (−70)
    • B. (−50) + (−70)
    • C. 50 − (−70)
    • D. (−50) + 70

    Choose the right answer

    Answer:

Part C: Word problems (4 marks each)

  1. 13.A mine's entrance is 120 m above sea level. A miner goes 290 m down from it. With sea level 0 and up positive, where is the miner now, in m?

    Working:

    Answer:

  2. 14.Ice at −26°C warms 2°C a minute. It must rise °C to reach 0°C, taking minutes.

    Fill in each blank

    Working:

    Answer:

  3. 15.A balance is −600 dollars. Each month $400 goes in and $150 is spent. How many months until it is no longer negative?

    Working:

    Answer:

  4. 16.A gull is 80 m above the sea and a fish 90 m below it. After the fish dives 15 m more, how far above the fish is the gull, in m?

    • A. 155
    • B. 170
    • C. 185
    • D. 10

    Choose the right answer

    Working:

    Answer:

  5. 17.City A is −7 hours, city B +1. It is 10:00 in A (24-hour clock). What hour is it in B?

    Working:

    Answer:

  6. 18.A balloon is 600 m up. Down 100 m: m up. Down 100 m more: m up.

    Fill in each blank

    Working:

    Answer:

Show the answers and working

Using directed numbers worksheet: Answers and working

Part A: Working out and filling in

  1. 1. 26°C

    15 − (−11) = 15 + 11 = 26. Up to 0°C first, then on to 15°C.

  2. 2. 3°C

    (−13) + 16 = 3, so 3°C. Rising goes up, not colder, and with different signs the sizes subtract. Until it reaches 0°C, it is still below zero.

  3. 3. −4°C

    (−12) + 8 = −4, so −4°C. Rising goes up, not colder, and with different signs the sizes subtract. Until it reaches 0°C, it is still below zero.

  4. 4. 100 dollars

    Profit is positive, loss negative: 750 + (−500) + (−150) = 100.

  5. 5. −300 dollars

    400 + (−700) = −300. Taking money out makes the balance smaller; the $400 it held goes against the withdrawal rather than being added on. If more came out than there was, it is a debt, written as negative.

  6. 6. −200 dollars

    Profit is positive, loss negative: 300 + (−350) + (−150) = −200.

  7. 7. 6 hours

    3 − (−3) = 3 + 3 = 6. They are on either side of 0, so add.

  8. 8. −12 points

    5 right: 5 × 1 + 17 × (−1) = −12.

  9. 9. 17 points

    23 right: 23 × 1 + 6 × (−1) = 17.

  10. 10. 5 hours

    4 − (−1) = 4 + 1 = 5. They are on either side of 0, so add.

Part B: Choose, or true or false

  1. 11. A. (−80) + (−50)

    With sea level 0 and up positive: start at −80, then change by −50: (−80) + (−50).

  2. 12. B. (−50) + (−70)

    With sea level 0 and up positive: start at −50, then change by −70: (−50) + (−70).

Part C: Word problems

Marking: 2 for the working, 1 for the answer, 1 for the sentence.

  1. 13. −170 m

    With sea level as 0: 120 + (−290) = −170.

  2. 14. 26, 13

    From −26°C to 0°C is a rise of 26°C, and 26 ÷ 2 = 13 minutes.

  3. 15. 3 months

    The net change is 400 − 150 = +250 a month. 600 ÷ 250 isn't whole, so round up: 3 months.

  4. 16. C. 185

    The fish is at (−90) + (−15). 80 − [(−90) + (−15)] = 185.

  5. 17. 18:00

    City B is 1 − (−7) = 8 hours ahead of city A: 10 + 8 = 18.

  6. 18. 500, 400

    600 + (−100) = 500; 500 + (−100) = 400.

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