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The time to plough a field varies directly as the area to be ploughed and inversely as...

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seerboldly | Student, Grade 10 | Salutatorian

Posted September 30, 2013 at 1:59 PM via web

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The time to plough a field varies directly as the area to be ploughed and inversely as the number of workers. If 8 workers can plought a 5 ha field in 6 houirs, how long will it take to plough a 10 ha field with 12 workers working at the same rate?

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llltkl | College Teacher | Valedictorian

Posted September 30, 2013 at 2:55 PM (Answer #1)

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This is a problem on compound proportion.

Let the area to be ploughed be Quantity 1,

the time to plough a field be Quantity 2 and

the number of workers be Quantity 3.

Quantity1(area)       Quantity2 (time)  Quantity3(no.ofworkers)

      5                                    

     10                                    x                                    12

According to the rule for solving compound proportions :

If quantity 1 and quantity 2 are directly related and quantity 2 and quantity 3 are inversely related, then we use the following rule:

`(6*8)/5=(x*12)/10`

`rArr 48/5=(12x)/10`

`rArr x=(48*10)/(12*5)=8`

Hence, it will take 8 hours to plough a 10 ha field with 12 workers working at the same rate

Sources:

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llltkl | College Teacher | Valedictorian

Posted September 30, 2013 at 2:59 PM (Reply #1)

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Addendum:

Please read the first line of the above table as:

Quantity1        Quantity2         Quantity3

     5                      6                      8

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