18. The scale of a map is [tex]1 \, \text{cm}: 8 \, \text{km}[/tex]. What area on the map would represent:

(a) [tex]64 \, \text{km}^2[/tex]
(b) [tex]128 \, \text{km}^2[/tex]
(c) [tex]320 \, \text{km}^2[/tex]
(d) [tex]1600 \, \text{km}^2[/tex]



Answer :

Let's solve the problem step-by-step for each part given the scale of the map which is [tex]\(1 \text{ cm} : 8 \text{ km}\)[/tex].

### Understanding the Scale

The scale [tex]\(1 \text{ cm} : 8 \text{ km}\)[/tex] means that 1 cm on the map corresponds to 8 km in reality. To find the area representation on the map, we'll follow these steps:

1. Calculate the side length [tex]\( \text{in km}^2 \)[/tex] of the given area.
2. Convert that side length from kilometers to centimeters.
3. Calculate the area in square centimeters.

### Given Areas

We are asked to find the area on the map for each of the following real-world areas:

[tex]\[ (a) \ 64 \text{ km}^2, \quad (b) \ 128 \text{ km}^2, \quad (c) \ 320 \text{ km}^2, \quad (d) \ 1600 \text{ km}^2 \][/tex]

### Step-by-Step Solution

#### (a) [tex]\(64 \text{ km}^2\)[/tex]

1. Find the side length (km):
[tex]\[ \sqrt{64 \text{ km}^2} = 8 \text{ km} \][/tex]
2. Convert side length to cm:
[tex]\[ \frac{8 \text{ km}}{8 \text{ km/cm}} = 1 \text{ cm} \][/tex]
3. Calculate the area on the map (cm[tex]\(^2\)[/tex]):
[tex]\[ (1 \text{ cm})^2 = 1 \text{ cm}^2 \][/tex]

So, the area on the map that represents [tex]\(64 \text{ km}^2\)[/tex] is [tex]\( 1 \text{ cm}^2 \)[/tex].

#### (b) [tex]\(128 \text{ km}^2\)[/tex]

1. Find the side length (km):
[tex]\[ \sqrt{128 \text{ km}^2} = 11.313708498984761 \text{ km} \][/tex]
2. Convert side length to cm:
[tex]\[ \frac{11.313708498984761 \text{ km}}{8 \text{ km/cm}} = 1.4142135623730951 \text{ cm} \][/tex]
3. Calculate the area on the map (cm[tex]\(^2\)[/tex]):
[tex]\[ (1.4142135623730951 \text{ cm})^2 = 2.0000000000000004 \text{ cm}^2 \][/tex]

So, the area on the map that represents [tex]\(128 \text{ km}^2\)[/tex] is approximately [tex]\( 2.000 \text{ cm}^2 \)[/tex].

#### (c) [tex]\(320 \text{ km}^2\)[/tex]

1. Find the side length (km):
[tex]\[ \sqrt{320 \text{ km}^2} = 17.88854381999832 \text{ km} \][/tex]
2. Convert side length to cm:
[tex]\[ \frac{17.88854381999832 \text{ km}}{8 \text{ km/cm}} = 2.23606797749979 \text{ cm} \][/tex]
3. Calculate the area on the map (cm[tex]\(^2\)[/tex]):
[tex]\[ (2.23606797749979 \text{ cm})^2 = 5.000000000000001 \text{ cm}^2 \][/tex]

So, the area on the map that represents [tex]\(320 \text{ km}^2\)[/tex] is approximately [tex]\( 5.000 \text{ cm}^2 \)[/tex].

#### (d) [tex]\(1600 \text{ km}^2\)[/tex]

1. Find the side length (km):
[tex]\[ \sqrt{1600 \text{ km}^2} = 40 \text{ km} \][/tex]
2. Convert side length to cm:
[tex]\[ \frac{40 \text{ km}}{8 \text{ km/cm}} = 5 \text{ cm} \][/tex]
3. Calculate the area on the map (cm[tex]\(^2\)[/tex]):
[tex]\[ (5 \text{ cm})^2 = 25 \text{ cm}^2 \][/tex]

So, the area on the map that represents [tex]\(1600 \text{ km}^2\)[/tex] is [tex]\( 25 \text{ cm}^2 \)[/tex].

### Summary

The areas on the map representing the given real-world areas are:

[tex]\[ (a) \ 64 \text{ km}^2 \rightarrow 1 \text{ cm}^2 \][/tex]

[tex]\[ (b) \ 128 \text{ km}^2 \rightarrow 2 \text{ cm}^2 \][/tex]

[tex]\[ (c) \ 320 \text{ km}^2 \rightarrow 5 \text{ cm}^2 \][/tex]

[tex]\[ (d) \ 1600 \text{ km}^2 \rightarrow 25 \text{ cm}^2 \][/tex]