Mrs. Corrubi takes 7.5 hours to complete the job alone.
Directly proportional: as one amount increases, another amount increases at the same rate. Direct variation means when one quantity changes, the other quantity also changes in direct proportion
Inversely Proportional: when one value decreases at the same rate that the other increases. An increase in the quantity A leads to a decrease in quantity B and vice versa.
Let the number of hours taken by Mrs Corrubi to do a particular work be x.
∴ The number of hours taken by Mr Corrubi to do a particular work will be 2x.
So according to the condition,
1/x + 1/2x = 1/5
(2+1)/2x = 1/5
3/2x = 1/5
2x = 15
x = 7.5 hours.
Thus Mrs. Corrubi takes 7.5 hours to complete the job alone.
Learn more about Direct and inverse Variations here :
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