Area to be painted = Area of walls + Area of ceiling
= 2(hl+hb)+lb
Where,
- H is height
- L is length
- B is breadth or width
In our case,
- H = 9 ft
- L = 20 ft
- B = 30 ft
Put the values in the formula ~
= 2(9×20+9×30)+20×30
= 2(180+270)+600
= 2×450+600
= 900+600
= 1500 ft²
Now,
Required number of cans = 1500/400 = 3.75
➪ Thus, she needs to buy 4 cans of paint...~