formula about when profit has covered cost

[zitafung]

it might be a simple question however i cannot figure out a formula to work the calculation automatically

i want to find out the month (in 1 decimal place) when i can recover the cost

e.g. the initial cost is $100 and then up till july, there are $97 accumulated profit. And per day profit in august is $22/ 31 days=$0.71. which means we need at least 5 more days to attain $3.55 more in order to reach $100 profit in total i.e. $97 + $3.55 = $100.55. and so 5/ 31 days = 0.16 month so altogether we need 7 + 0.16 =7.16 and (in 1 decimal place) i.e. 7.2 months in order to reach $100 profit.

so can you kindly help if there's any formula available for this?

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excel question.xls

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