How to find/calculate currency price from other currency

 
I am working on project where i have All EUR currency, and i need to find another price from EUR

Example: There are two currency that values I have EURUSD and EURAED.
I need to find USDAED, Formula: EURAED/EURUSD = USDAED

But the close price must be equal or between HIGH & LOW prices but after calculation its changes.

"All prices updated time is same"


Problem:
* Many currency close price is less then Low or high then High.
* First tick, High is high, then next tick, high less than last high.


Question:
Which is the correct way to find currency prices from other currencies?