One, if it is the correct USA amount; see the Universal Postal Union of 1949.
one
The number of stamps that you need to send a letter from Australia to London, will depend with the value of one stamp.
4
One stamp.
3 stamps. An average stamp is $0.44 so one would need $1.32 to send a letter from London to Utah.
1 oz letter to UK is .94
Nine
One first class postage.
$1.05 = Forever stamps are worth 45 cents each. so a little more than two of these stamps
USPO stamp rates are higher in 2014. To mail a letter to Arizona from Michigan costs one 48 cent stamp.
It depends on the size and weight, but if it's a regular letter, a 44-cent stamp will suffice.
TWO US Forever stamps will suffice (USA to London post card)