Scheduling and ordering constraints: Practice 1

10 original teaching questions with answers and explanations.

Instructions for this set

Use only the stated constraints. Before does not mean immediately before. Tasks use one slot each unless durations or parallel resources are explicitly given.

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  1. 1. Four tasks A, B, C and D occupy four slots. A is first, D last, and B is before C. Which task is third?
    1. C
    2. D
    3. A
    4. B

    Reference: q-77caa64e-104 · Report this question

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    Answer: A. C

    The fixed endpoints leave slots two and three for B and C. Their order forces C into slot three.
  2. 2. Tasks P, Q and R each take 20 minutes and run sequentially from 09:00 with no gaps. P is first and R last. When does Q start?
    1. 09:00
    2. 09:20
    3. 09:40
    4. 10:00

    Reference: q-43695cb-126 · Report this question

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    Answer: B. 09:20

    P occupies 09:00 to 09:20. Q is the middle task, so it starts at 09:20.
  3. 3. Five speakers use slots 1 to 5. Mina is in slot 2. There are exactly two speakers between Mina and Noah. Which slot does Noah occupy?
    1. 3
    2. 4
    3. 5
    4. 1

    Reference: q-fc5c4044-134 · Report this question

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    Answer: C. 5

    A separation of two intervening speakers means a position difference of three. From slot two, only slot five is valid.
  4. 4. Three tasks A, B and C each occur once. A must be before C; B has no restrictions. Which order is invalid?
    1. A B C
    2. B A C
    3. A C B
    4. C A B

    Reference: q-bd0d11d3-107 · Report this question

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    Answer: D. C A B

    C A B places C before A, violating the only precedence requirement. The other orders satisfy A before C.
  5. 5. A 45-minute meeting starts at 10:15. A 15-minute break follows. What is the earliest next start time?
    1. 11:15
    2. 11:30
    3. 10:45
    4. 11:00

    Reference: q-2b57a550-102 · Report this question

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    Answer: A. 11:15

    The meeting ends at 11:00. Add the 15-minute break to get 11:15.
  6. 6. Tasks X and Y each need the same single machine for 30 minutes. Both are ready at 08:00 and cannot overlap. What is the earliest time both can finish?
    1. 08:45
    2. 09:00
    3. 09:30
    4. 08:30

    Reference: q-8e4a549d-151 · Report this question

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    Answer: B. 09:00

    One machine processes the two half-hour tasks sequentially, requiring one hour from 08:00.
  7. 7. Task A takes 40 minutes and task B takes 25. They use independent machines and start together at 14:00. When are both complete?
    1. 15:05
    2. 14:25
    3. 14:40
    4. 15:00

    Reference: q-9642b4c2-128 · Report this question

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    Answer: C. 14:40

    Parallel completion time is the longer duration, 40 minutes. Both are complete at 14:40.
  8. 8. Four interviews occur in slots 1 to 4. R is immediately before S. R is in slot 3. Which slot holds S?
    1. 1
    2. 2
    3. 3
    4. 4

    Reference: q-be69c200-102 · Report this question

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    Answer: D. 4

    Immediately after slot three is slot four. No other position satisfies adjacency in this direction.
  9. 9. In a four-task sequence, A is before B, B before C, and C before D. How many valid orders are possible?
    1. 1
    2. 2
    3. 4
    4. 6

    Reference: q-9436feb5-104 · Report this question

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    Answer: A. 1

    The full precedence chain fixes A B C D. There is exactly one valid order.
  10. 10. Five checks run sequentially from 13:00. Each takes 12 minutes, and there are no gaps. When does the fifth check start?
    1. 13:36
    2. 13:48
    3. 14:00
    4. 14:12

    Reference: q-aed375c1-120 · Report this question

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    Answer: B. 13:48

    Four earlier checks consume 4 times 12 = 48 minutes. The fifth starts at 13:48, not at the completion time 14:00.

Review your method

Return to the scheduling and ordering constraints lesson and identify the reasoning step behind each mistake before repeating the set.

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