It takes for three gardeners 90 minutes to weed a garden. If the job is to be done in only 15 minutes, how many more gardeners need to be put on the jobs?
each gardener takes 3*90 = 270 minutes to do the job alone.
So, since 15 = 270/18
It will take a total of 18 gardeners.
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To determine how many more gardeners need to be put on the job, we can use the concept of worker-hours. Worker-hours represent the amount of work done by a single worker in an hour.
Given that three gardeners can complete the job in 90 minutes, we can calculate the worker-hours required to complete the job as follows:
Worker-hours = Number of Gardeners × Time (in hours)
Since there are three gardeners and each hour has 60 minutes, we can express 90 minutes as 90/60 = 1.5 hours.
Worker-hours = 3 × 1.5 = 4.5
Therefore, three gardeners collectively contribute 4.5 worker-hours to complete the weeding job.
Now, let's determine how many gardeners are needed to accomplish the job in 15 minutes.
Worker-hours = Number of Gardeners × Time (in hours)
Since the time given is 15 minutes, we need to convert it into hours by dividing by 60:
Time (in hours) = 15/60 = 0.25 hours
Now we can rearrange the above formula to find the number of gardeners:
Number of Gardeners = Worker-hours / Time (in hours)
Number of Gardeners = 4.5 / 0.25 = 18
Therefore, to complete the job in only 15 minutes, an additional 18 gardeners need to be put on the task.