$7.20/60 oz = 12 cents per ounce.
Just a single ounce. The second ounce will cost 20 cents.
For a regular sized envelope up to 3.5 ounces, it is 98 cents for the first ounce and 84 cents for each additional ounce or fraction of an ounce.
The first ounce will cost 44 cents. Each additional ounce, or fraction, is another 17 ounces. That would be 78 cents for that envelope at the start of 2011.
That is 7,680 ounces.
1 ounce is 0.9115 troy ounces.
6200 cents
"Tri-ounce" is not a standard unit of measurement. If you meant to ask about "three ounces," then there are three ounces in three ounces.
960 ounces
62 = .62 or sixty-two cents
The first ounce will cost 44 cents. Each additional ounce, or fraction of an ounce, is 17 cents. The total will be 95 cents for a 3.4 ounce letter.
An ounce is 1 ounce, what else could it be.
Typically you will need six stamps. The first ounce will go for the standard first class postage rate. The second through six ounces will go for a reduced rate. Currently that would be 45 cents for the first ounce and 20 cents each for the additional ounces. The total would be $1.45.