Measurement

Chapter 8

Outcomes D1: solve indirect measurement problems, using proportions D2: solve measurement problems, using appropriate SI units D3: estimate areas of circles D4: develop and use the formula for the area of a circle D5: describe patterns and generalize the relationships between

areas and perimeters of quadrilaterals and areas and circumferences of circles

D6: calculate the areas of composite figures D7: estimate and calculate surface areas and volumes of right

prisms and cylinders D8: measure and calculate surface areas and volumes of

composite 3-D shapes

Metric Conversions

Metric units are very nice to work with, since they are all multiples of ten of each other.

The basic units are meters (for length), grams (for mass or weight), and liters (for volume).

Metric Prefixes

We use the following prefixes to describe the units we are dealing with:• kilo-, hecto-, deka-, deci-, centi-, and milli-.

• To convert between the various prefixes, just move up and down this list of prefixes, moving the decimal point as you go.

Metric Staircase

kilo .001 hecto .01 decimal point moves to the right

deka .1Basic Unit (m, l, g) 1

deci 10

centi 100

decimal point moves to the left milli 1000

Example:

Since each step is ten times or one-tenth as much as the step on either side, we have:• 1 kilometer = 10 hectometers

You try these…

1) 2.5 km = ? m

2) 100cm = ? km

3) 5m = ? mm

What is perimeter?

Perimeter is the sum of the lengths of all the sides of a polygon.• It is the total length around an object.

Example…

Find the perimeter of the rectangle with side lengths of 4m and 2m.

2m

4 m

The perimeter would be 2m + 4m + 2m + 4m = 12m

What is area? Area is the number of square units needed to cover

a surface. 2m

4m

The area of this rectangle can be found by using the equation A = l x wTherefore A = 4m x 2m

= 8m2

You try these…(find area and perimeter)

1) Rectangle with sides 3cm and 7cm

2) Square with sides 5m

3) Rectangle with sides 4m and 3m

What about triangles???

Can you use the same formulas for a triangle?

Area of a triangle

Area of a triangle is

A = ½ b x h

8cm

4cm

Area = ½ (4cm)(8cm) = 16cm2