Question 1021569
(1/21 per member)/(45 days)=1/945 bridge per man per day
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2/3 bridge is 630/945 of the bridge:
At 1/945 bridge per man-day, we need 630 man-days in 42 days
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630 man-days/42 days=15 men.
We need 15 painters to finish in time, and we have 7 men,
so we need 8 additional men.