SOLUTION: I exchanged sterling into euros, where the rate was 1.17 to exchange GBP into euros and 1.35 to exchange euros back to sterling. I bought a guaranteed buyback for �3.99 for a g'tee

Question 607585: I exchanged sterling into euros, where the rate was 1.17 to exchange GBP into euros and 1.35 to exchange euros back to sterling. I bought a guaranteed buyback for �3.99 for a g'teed buy back rate of 1.17 euros to GBP. I have tried to work out what minimum number of euros i need to exchange back to GBP to ensure that I don't lose out on the �3.99 paid for the guarantee. I have worked out manually without an algerbaic formula that I need to exchange no less than 35 euros to ensure the saving is at least �3.99. However I cannot seem to work out a formula which determines this exactly. I've tried 3.99/.18 ie the difference in the exchange rate, but this only gives me �22.16, which whem i use the 1.17 I only get 22.16*1.17=18.94 and 22.16/1.35=16.41, which is not the required difference of 3.99 ie the cost of the guarantee. I know that if i use 35 euros, I get 25.92/29.92, the difference I am looking for, but how do I determine this algebraically?
Answer by scott8148(6628) (Show Source): You can put this solution on YOUR website!
you are looking to get �3.99 MORE from the better exchange rate

(� / 1.35) + 3.99 = � / 1.17
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