I think it's 36.5 or 37 full cans of paint

1. Floor and ceiling=20*15=300-->*2=600-->*2=1200 (2 coats of paint)
2. Two walls with dimensions 20*9=180-->*2=360-->*2=720
3. Two walls with dimensions 15*9=135-->*4=540

So, 1200+720+540=1460
1460/400=36.5

Wall 1: 9 x 15 = 135 sq ft
Wall 2: 9 x 20 = 180 sq ft
Ceiling: 15 x 20 = 300 sq ft

2 x (2 x wall 1 + 2 x wall 2 + ceiling)
= 2 x ( 2 x 135 + 2 x 180 + 300 )
= 2 x ( 270 + 360 + 300 )
= 2 x 930
= 1860 sq ft of paint

Need 5 full cans of paint (1860/400 = 4 13/20 < 5)

moutar wrote:Wall 1: 9 x 15 = 135 sq ft
Wall 2: 9 x 20 = 180 sq ft
Ceiling: 15 x 20 = 300 sq ft

2 x (2 x wall 1 + 2 x wall 2 + ceiling)
= 2 x ( 2 x 135 + 2 x 180 + 300 )
= 2 x ( 270 + 360 + 300 )
= 2 x 930
= 1860 sq ft of paint

Need 5 full cans of paint (1860/400 = 4 13/20 < 5)

Nope. That's not correct, but you're close!

lilu wrote:I think it's 36.5 or 37 full cans of paint

1. Floor and ceiling=20*15=300-->*2=600-->*2=1200 (2 coats of paint)
2. Two walls with dimensions 20*9=180-->*2=360-->*2=720
3. Two walls with dimensions 15*9=135-->*4=540

So, 1200+720+540=1460
1460/400=36.5

Please don't tell me we're painting the floor as well.

moutar wrote:Please don't tell me we're painting the floor as well.

haha, why not?

If we paint the floor as well then its 6.15 gallons of paint.

Thanks
raama

How many gallon cans of paint will be needed to give 2 coats of paint the walls of 15'x20' room with 9' ceiling? A gallon of paint covers 400 sq. ft.

I think there is neither need to paint ceiling nor floor

1wall = 20*9=180
2wall = 15*9=135

each wall is doubled so =180*2 + 135*2=630 for 1 coat
for 2 coat = 630 * 2 = 1260 ft^2
1 gall can cover 400 ft^2 so 1260/400 ~ 3....
thus we need 3-4 gallon of paint

6.15 gallons of paint.


total surface area =1230sqft

400sqft requires 1 gallon paint

hence 1230sqft will require 3.075 gallons.

for 2 coats 2* 3.075 = 6.15 gallon.

S0laris wrote:How many gallon cans of paint will be needed to give 2 coats of paint the walls of 15'x20' room with 9' ceiling? A gallon of paint covers 400 sq. ft.

I think there is neither need to paint ceiling nor floor

1wall = 20*9=180
2wall = 15*9=135

each wall is doubled so =180*2 + 135*2=630 for 1 coat
for 2 coat = 630 * 2 = 1260 ft^2
1 gall can cover 400 ft^2 so 1260/400 ~ 3....
thus we need 3-4 gallon of paint

I think this is the correct solution.
The question asked about painting the Walls. So floor and ceiling are not included.

This problem brings out an important mistake that we are all likely to commit.

The following process can eliminate this problem.
1. translate the problem to the scratchpad as ur are reading it. (esp those long winded problems)
2. when u read the Q prompt, read it twice and write it down.
3. Solve the problem.
4. read the Q again to confirm that the answer really answers the Q.
(I follow step 4 for atleast the first 10 problems to get to the rhythm)

vittalgmat wrote:

S0laris wrote:How many gallon cans of paint will be needed to give 2 coats of paint the walls of 15'x20' room with 9' ceiling? A gallon of paint covers 400 sq. ft.

I think there is neither need to paint ceiling nor floor

1wall = 20*9=180
2wall = 15*9=135

each wall is doubled so =180*2 + 135*2=630 for 1 coat
for 2 coat = 630 * 2 = 1260 ft^2
1 gall can cover 400 ft^2 so 1260/400 ~ 3....
thus we need 3-4 gallon of paint

I think this is the correct solution.
The question asked about painting the Walls. So floor and ceiling are not included.

This problem brings out an important mistake that we are all likely to commit.

The following process can eliminate this problem.
1. translate the problem to the scratchpad as ur are reading it. (esp those long winded problems)
2. when u read the Q prompt, read it twice and write it down.
3. Solve the problem.
4. read the Q again to confirm that the answer really answers the Q.
(I follow step 4 for atleast the first 10 problems to get to the rhythm)

Excellent tip! Thanks for sharing with us.

OA is 4 gallons since when you buy the paint you buy in whole. Hence, the answer is ~4 gallons.