3.2

How Can I Measure An Object?

Pg. 7Units of Measure

3.2 – How Can I Measure an Object?______Units of Measure

How tall are you? How large is the United States? How much water does your bathtub at home hold? All of these questions ask about the size of objects around you. How can we answer these questions more specifically than saying "big" or "small"? Today you will be investigating ways to answer these and other questions like them.

3.13 – UNITS OF LENGTHLength often provides a direct way to answer the question, "How big?" In this activity, your teacher will give your team rulers with a unit of length to use to measure distances. For instance, if you have an object that has the same length as three of your units placed next to each other, then the object's length is "3 units."

a. Common units you may have used before are inches or meters. Today you are going to measure in inches or centimeters, based on your teachers assignment.

Team Captains and Facilitators – Centimeters

Reporters and Resource Managers – Inches

b. Find the dimensions of the shape at right using your unit of length. That is, how wide is the shape? How tall? Compare your results with those of other teams.

MURAL

1 2 3 4 5 6

12

34

5

9.7cm

Width: Height:

3.8 in

8.7 cm

3.5 in

c. The local baseball club is planning to make a mural that is the same general shape as the one you measured above. The club plans to frame the mural with neon tubes. Approximately how many units of neon tube will they need to do this?

1 2 3 4 5 6 71

23

45

1

2

3

31.7 cm

Perimeter:

12.8 in

d. To paint the mural, the wall must first be covered with a coat of primer. How much of the wall will need to be painted with primer? Remember that the measurement of the region inside a shape is called the area of the shape. What is the approximate area of the mural? That is, how many of your square units fit within your shape?

1 2 3 4 5 6

12

34

5

Area:

55.2 cm2

10.5 in2

Perimeter: Length around a shape.

Measured in ucm, in, ft, yd

Area: Square units inside a shape.

Measured in u2

cm2, in2, ft2, yd2

1u1u21u

1u1u21u

1u1u21u

1u1u21u

1u1u21u

1u1u21u

3.4 –COMPOSITE SHAPESFind the perimeter and/or total area of the shaded figures. Show all work.

6

3

6

3

6+3+6+3 = 18un

(6)(3) = 18un2

7

6

2

25

4

26 un

7

6

2

25

4

26 un

2012

32 un2

23

32 un

1524

39 un2

99

9

6

6

6

90 un

324 un2

256 un2

(24)(12) – (8)(4)288 – 32

3.15 –WORKING BACKWARDSGiven the area of the shape, find the missing side length. Don’t forget units.

A = bh126 = (18)(x)

18 18

x = 7 ft

A = bh64 = x2

x = 8 in

A = bh14 = x(x-5)

14 = x2 – 5x

0 = x2 – 5x – 14 xx

-7+2

(x-7)(x+2) = 0

x = 7mi x = -2mi