What share of her mother’s cost is Ana’s profit?
=> Her mothers costs are 100%. We need to find Ana's Profit relative to those 100%.
Ana’s Profit (relative to her mothers cost) = Revenue - Cost = Revenue - 115% = ???
We can calculate Ana's Revenue by using the calculation formula for her Profit Margin:
Profit Margin = Profit / Revenue
Profit Margin = (Revenue - Cost) / Revenue
30% = (Revenue - 115%) / Revenue
30% * Revenue = Revenue -115%
70% * Revenue = 115%
Ana’s Revenue = 164,29% (rel. to her mothers cost)
This means Ana sells the cookies for 164,29% of the price that her mother paid to prepare them.
Ana’s Profit relative to her mothers cost is therefore: Profit = Revenue - Cost = 164,29% - 115% = 49,29%