To add to bartzilla's post above:
Freeing memory on iOS works by (taking educated guess here) the 'free memory' app requesting a very large amount of RAM. What happens here is that iOS then tries to free up as much RAM in any app that isn't running and then that app basically releases that memory it requested, leaving you with a bunch of free memory.
But you know how else you can free memory...without buying apps and by looking at pretty charts? It's called opening the app you want and iOS free memory for you! Amazing. Using a free memory app basically kills multitasking apps, basically meaning you lose sleeping apps. Just be patient for a moment as memory is freed up when you load your game, it'll smooth out in about the same time as it took for you to open the free memory app.