Two women, Ganga and Saraswati, working separately can mow a field in 8 and 12 hours respectively. If they work in stretches of one hour alternately, Ganga beginning at 9 a.m., when will the mowing be finished?
answer is 6:30 pm. Please explain me how do we solve this question. Please explain each step very clearly. thank you so much!
answer is 6:30 pm. Please explain me how do we solve this question. Please explain each step very clearly. thank you so much!
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Hi Gracy
Ganga can mow the entire field in 8 hours
so, if she works for 1 hour she'll mow 1/8 of the field
Similarly
Saraswati will mow in 1 hour 1/12 of the field
So in 2 hours they will mow 1/8 + 1/12 = 5/24 of the field
so in 8 hours they would have mowed (5/24)*4 = 20/24 of the field
The remaining unmowed part of the field = 1 - 20/24 = 4/24 = 1/6
The 9th hour Ganga will complete 1/8 of the field
so
balance unmowed area = 1/6 - 1/8 = 1/24 of the area
Saraswati can mow 1/24 of the area in half an hour.
So total time taken = 9.5 hours from 9 amm = 6:30 pm
Shy
Ganga can mow the entire field in 8 hours
so, if she works for 1 hour she'll mow 1/8 of the field
Similarly
Saraswati will mow in 1 hour 1/12 of the field
So in 2 hours they will mow 1/8 + 1/12 = 5/24 of the field
so in 8 hours they would have mowed (5/24)*4 = 20/24 of the field
The remaining unmowed part of the field = 1 - 20/24 = 4/24 = 1/6
The 9th hour Ganga will complete 1/8 of the field
so
balance unmowed area = 1/6 - 1/8 = 1/24 of the area
Saraswati can mow 1/24 of the area in half an hour.
So total time taken = 9.5 hours from 9 amm = 6:30 pm
Shy
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we multiply by 4 to get 5 as close to 24 as possible. 4*5 = 20 but 5*5 = 25 which is greater than 24
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