Exercise 4 Page 168

Practice makes perfect

a We know that each unit on the diagram represents 20 feet. Therefore, by counting the number of units on the horizontal axes, we can find the length of the field.

The football field stretches 18 units on the diagram's horizontal axis. Since 1 unit=20 feet, the length of the field is the product of the number of units and the length of each unit. 18* 20=360 feet

b To find the perimeter of the field, we have to add up its four sides. We know that the length of the field is 360 feet. The field has two sides of this length, so let's add these two lengths.

360+360=720 feet We also need to add the distance of the field's shorter sides which we will call the width. Let's measure the number of units on the vertical axis in our diagram.

The football field stretches 8 units on the diagram's vertical axis. Since 1 unit=20 feet, the width is the product of the number of units by the width of each unit. 8* 20=160 feet Let's add the distance of the widths to the sum of the longer sides. 720+160+160=1040 feet The perimeter of the field is 1040 feet.

c To determine if the school has enough money, we first have to find out how many square feet of turf we need. This is equal to the area of the rectangular football field. We can determine this by multiplying the length by the width.

A= l * wLet's substitute the width and length of the football field into the formula for the area of a rectangle.

A= l * w

SubstituteII

l= 360, w= 160

A= 360* 160

Multiply

A=57 600

We have to cover 57 600 square feet with turf. If each square foot of turf costs $2.69 the total cost will be the product of the number of square feet and the cost per square feet. 57 600* 2.69= $ 154 944 The budget is not enough.

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Exercises p.168-169

Exercise 4 Page 168

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