4. .5 per ounce so 3.5 for 7 ounces
5. 7.5 degree every hour so 22.5 for 3 hours
6. 61 miles per hour so 305 for 5 hours
The answer is 6480.
Length: 6x3=18
Width: 4x3=12
Height:10x3=30
LengthxWidthxHeight=18x12x30=6480
Let's assume length of the room as y
so the width of the room = y - 5
Area
y * (y - 5) = 750
Each tray is 1/5 purple. So one tray is 1/5 purple, and if you add another tray, you're adding the same amount of each color, so it's now 2/10 purple, which simplifies to 1/5. No matter how many you add, the fraction will be 1/5.