In the first month, the price of the iPhone fell by 10/100*$1000=$<<10/100*1000=100>>100
The new price after the first month is $1000-$100 = $<<1000-100=900>>900
In the second month, the price fell 20% further by 20/100*$900 = $<<20/100*900=180>>180
The new price after the second month is $900-$180 = $<<900-180=720>>720
#### 720