I will answer this by first converting the measurements to yards, but you could also calculate the area in feet and then convert to square yards when finished (as I will also show). There is no right or wrong way to do it.
12 feet = 12/3 = 4 yards
21 feet = 21/3 = 7 yards
Thus the area of the room = 4 * 7 = 28 square yards.
The other way to calculate this is to work in feet initially, thus 12 * 21 = 252 square feet. 1 square yard = 3 * 3 = 9 square feet. Thus the area = 252/9 = 28 square yards.
30*25=750 square feet To convert this to yards, divide by 3. 750/3=250 square yards
12*50/6=100 100 square yards
120ft^2 , 10ft * 12ft
A yard is a unit of length. A square foot is a unit of area. The two units are therefore incompatible.
L x W / 9 = sq yards Multiply the length times the width and divide by 9 to get the square yards. Just remember, the amount you have to buy may be more depending on the size of your room and the sizes of the rolls of carpet available.
30*25=750 square feet To convert this to yards, divide by 3. 750/3=250 square yards
I assume that the room has at least one door, which you may not wish to paper over and possibly some windows. Also you will probably not wish to paper the floor. If you paper the ceiling as well as the walls, then you will require at most 44 square yards, whereas if you do only the walls, you will require less than 28 square yards.
12*50/6=100 100 square yards
96.
9.2 square meters.
7560 cubic yards of air 30 x 28 x 9 = 7560
120ft^2 , 10ft * 12ft
A yard is a unit of length. A square foot is a unit of area. The two units are therefore incompatible.
L x W / 9 = sq yards Multiply the length times the width and divide by 9 to get the square yards. Just remember, the amount you have to buy may be more depending on the size of your room and the sizes of the rolls of carpet available.
4.25 yards.
A yard is 3 feet so your room is 3 by 4 yards which is 12 sq yards. However, most carpet comes in widths of 13 feet so you may have to pay for 9 feet by 13 feet - as your supplier when getting a quote.
105 yards.