15 cm^2
It is: 30*15*12 = 5400 cubic cm
15 cm for the diagonal.
It is 3 cm * 9cm = 27 cm2.
The ratio is 3:2
15 cm long and 5 cm wide is pretty nearly 15 cm long.
10 cm wide and 15 cm long
15 cm^2
50
It is: 30*15*12 = 5400 cubic cm
Area = 15*12 = 180 square cm
1,620
Multiply 20 x 15 x 78 = 23400 cubic cm = 1428 cubic inches
A queen-size mattress is 60" wide by 80" long (152 cm wide by 203 cm long). A king-size mattress is 76" wide by 80" long (193 cm wide by 203 cm long). A California king-size mattress is 72" wide by 84" long (182 cm wide by 213 cm long).
It is an area measurement. Think of taking 15 1x1 cm square tiles and putting them all in a row. The area of that row if 15 cm long and 1 cm wide so it is 15 cm squared.
Roughly 140 cm wide by 190 cm or 200 cm long 160 cm wide by 190 cm or 200 cm long (closest to North American Queen, which is 153 cm wide by 203 cm long)
15 cm for the diagonal.