# Thread: need help with concrete and pathway problem

1. ## need help with concrete and pathway problem

Chris wants to put a concrete path and a fence around his rectangular garden. The concrete path will be 1 metre wide and the fence will go around the edge of the path. The garden itself measures 5 metres by 8 metres.
(a) Calculate the length of the fence.
(b) Calculate the area of the concrete path.
(c) If the thickness of the concrete path is 60 mm, calculate the volume of concrete needed.

2. i have got 7m by 2= 10m2 for a and for b 40 metres and c 2.4 m

3. I'm afraid none of your answers are right. First, you need to make a diagram. Here, I made one for you (sorry it's a little small):

The length of the fence (in brown) would be the perimeter of the outer rectangle. Given that the inner rectangle (the garden) has dimensions of 8m x 5m, and that the walkway is 1m all around, can you figure out the length and width of the outer rectangle (marked with "?")? When you figure that out, you can now find the perimeter of the outer rectangle, and that will be your answer for (a).

(b) First, the units for area in this problem is square meters. So you would have to write $\displaystyle \text{m}^2$ as your unit. Second, it looks like you found the area of the garden, not the concrete path.

From part (a), you now know the length & width of the outer rectangle. You can also find the area. But this area would be the area of the concrete walkway and the garden combined. That's not what we want. We want the area of just the concrete walkway. So how do I get this? Hint: you'll need to know the area of the garden, too.

(c) You have the right idea that you'll need to multiply the area of the concrete walkway by the thickness to get the volume, but of course you had the wrong answer for (b). And you converted 60mm to meters, that was good. But don't forget that here the units for volume would be is cubic meters. So you would have to write $\displaystyle \text{m}^3$ as your unit.