ITPEC IP April 2024 Question 67
ITPEC IP April 2024 — Question 67 of 100
The minimum completion sequence is C, then A, then B: C → A → B. For a two-machine flow shop, Johnson's rule places an activity with the smallest time on machine X as early as possible and one with the smallest time on machine Y as late as possible. The overall smallest time is B's 5 minutes on Y, so B goes last. The next smallest is C's 6 minutes on X, so C goes first, leaving A in the middle.
The resulting schedule is: C uses X from 0–6 and Y from 6–14; A uses X from 6–14 and Y from 14–24; B uses X from 14–24 and Y from 24–29. All work finishes at minute 29.
Answer (c)
Why not others: The other orders create more idle time on Y or delay the final short Y operation, giving a makespan longer than 29 minutes.
Key rule: In a two-machine flow shop, schedule the smallest X time toward the front and the smallest Y time toward the back.
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