6 hours 36 minutes, or 6 hours 31 1/2 minutes
Dividing the task among the 6 committee members means each member will be making 525/6 = 87.5, that is, either 87 or 88 flowers. (We doubt that two people working together on the same flower will finish it in half the time.)
Each of the three committee members making 88 flowers will take ...
... 88 × 4 1/2 minutes = 396 minutes = 6 hours 36 minutes
Each member making 87 flowers will be finished 4 1/2 minutes sooner, after 6 hours 31 1/2 minutes.
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Comment on the problem
This problem seemingly invites you to divide the labor evenly among committe members. Doing that would give you an answer of 6 hours 33 3/4 minutes. You need to ask yourself whether that is practical for this situation.
