12 days because the walls would be four times as big as the first room.
If the walls are 10 ft x 10 ft, then each wall has 100 square feet. Adding the four walls makes 400 square feet to paint. Doubling the width and height of the walls to 20 ft x 20 ft means each wall is now 400 square feet, for a total of 1600 square feet to paint. 1600 ft is four times 400 square feet, thus if it took him 3 days to paint 400 square feet, it will take 12 days (or four times as much) to paint 1600 square feet.
11 Comments on "Painting a Bigger Room"
Mark W Allen says
August 19, 2017 @ 00:28
Do you mean a room twice the size?
In which case, the walls would be 8 times as large, unless I’m misunderstanding your question:
Twice the length = (3 + 3) + twice the width =(3 + 3) + twice the height = (3 +3 +3 + 3) = 24 days?
Love your puzzles, btw!
August 19, 2017 @ 19:58
You’re right, the dimensions should just be width and height, since you only paint the walls, not the floors and ceilings.
Lalit Nijhawan says
August 20, 2017 @ 00:59
Vishal Garg says
August 22, 2017 @ 00:24
I think some confusion is here with the question. If painter paints a room in 3 days that means he is painting 4 walls in 3 days, for simplicity, if we consider that he is painting in 4 days, then we can assume he is painting 1 wall per day. Now the size of wall is doubled, so he will paint one wall in 2 days. That means he will take 8 days to paint all 4. It can be concluded that time is doubled (4 to 8), so he will take 6 hours not the 12. Please correct me if I misunderstood.
November 27, 2017 @ 18:45
I disagree with the stated answer… Unless he’s painting floors… If walls, then he paints 4 of them (the perimeter of a square) in 3 days… Doubling the width and length of the room may quadruple it’s area, but the bounding wall would only double in size. So it would take 6 days to do twice the work. (Btw… This is one SLOW painter!)
November 28, 2017 @ 09:46
You are free to disagree, but it’s basic math. If the walls are 10 ft x 10 ft, that’s 100 square feet per wall. Four walls makes 400 square feet to paint. Doubling the width and height of the walls to 20 ft x 20 ft means each wall is 400 square feet, for a total of 1600 square feet to paint, or four times the initial area. Thus it will take four times as long to paint.
J J says
April 11, 2018 @ 00:27
If the walls are 10 ft x 10 ft, that’s 100 square feet per wall. Four walls makes 400 square feet to paint. Doubling the width of the room makes two walls 10 ft x 20 ft. Same for the length of the room. Notice the height if the walls don’t change. This means each wall is 200 square feet, for a total of 800 square feet to paint, or two times the initial area. Thus it will take two times as long to paint.
April 11, 2018 @ 10:12
A 10′ x 20′ room is not twice the size of a 10′ x 10′ room.
J J says
April 11, 2018 @ 12:54
Let’s try again.
A 10’x10′ room has a perimeter of 40′. A 20’x20′ room has a perimeter of 80′. Twice as much wall, twice as much time.
December 27, 2019 @ 23:49
3 days to paint a room no mention of size aka size doesnt matter
August 25, 2020 @ 02:43
3 days to paint a room… Big or small it’s 3 days per room.
Like a ton of bricks or a ton of feathers… Both weigh a ton.
Leave a comment