Area Day 2

Math 10-3

Ch. 3 Measurement

Ex1. Determine the area of the following shape.

*First, find the formula for the area of a TRIANGLE: Area triangle = b x h

Fill in the formula with the information from the diagram.

ATri = x 8 ft x 3 ft

Now solve. *remember, multiplying by is the same as dividing by 2!

8 x 3 2 = 12 ft2

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Ex2. Determine the area of the following shape.

*First, find the formula for the area of a PARALLELOGRAM: Area Parallelogram = b x h

Fill in the formula with information from the diagram:

Ap = b x h = 12 cm x 7 cm = 84 cm2

Ex3. Determine the area of the following shape.

First, find the formula for the area of a TRAPEZOID: Area Trapezoid = (b1+b2) x h

Fill in the formula with information from the diagram:

ATrap = (9 mm + 4 mm) x 3 mm

*First, you must add (9 + 4) because they are in BRACKETS. Remember BEDMAS?

9 + 4 = 13 13 x 3 2 = 19.5 mm2

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Ex4. The area of a triangle is 12 in2. If the base of the triangle is 6 in long, what is the height of the triangle?

ATriangle = 12 in2 b = 6 in h = ?

We are looking for the height!

Fill in the formula for area of a triangle with what we already know:

ATriangle = b x h 12 in2 = 6 in x h 2 What is the opposite of dividing by 2? Multiply by 2 on the other side!

12 x 2 = 6 x h 24 = 6 x h

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Ex4. The area of a triangle is 12 in2. If the base of the triangle is 6 in long, what is the height of the triangle?

24 = 6 x h

What is opposite of multiplying by 6? Divide by 6 on the other side!

24 6 = h

h = 4 in

Double check to make sure:

ATriangle = b x h = 6 x 4 2 = 12 in2

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Ex5. The area of a square is 16 cm2. What is the length of one side?

Fill in the formula for area of a square with what we already know:

ASquare = s2

16 cm2 = s2

But we don’t want s2 we want just s !

What is the opposite of squaring something? Square rooting!

Find the button on your calculator. This is the operation you use to “un-square” a number.

16 = s2

= s

s = 4 cm

Double check to make sure:

Asquare = s2 = s x s = 4 x 4 = 16 cm2

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How do we convert between SI square units?

Remember, the SI measuring system is based on 10.

Ex6. 8 m2 is how many cm2?

HAVE m2 WANT cm2

Start at m2 and follow the arrows to cm2 we have to multiply by 102 twice!

*Remember 102 is the same as 10 x 10 !

8m2 x 102 x 102 = 8 m2 x 10 x 10 x 10 x 10 = 80000 cm2

Ex7. 350 mm2 is how many dm2?

HAVE mm2 WANT dm2

Start at mm2 and follow the arrows to dm2 we have to divide by 102 twice!

350mm2 102 102 = 350 10 10 10 10 = 0.035 dm2

How do we convert between Imperial square units?

Remember, the Imperial Measurement System is based on referents!

Ex8. 9 yd2 is how many in2?

HAVE ft2 WANT in2

Start at yd2 and follow the arrows to in2 We have to x 32 and then 122 !

9 yd2 x 32 x 122 = 9 yd2 x 3 x 3 x 12 x 12 = 11664 in2

Ex9. 2 016 in2 is how many ft2 ?

HAVE in2 WANT ft2

Start at in2 and follow the arrows to ft2 We have to divide by 122!

2016 in2 122 = 2 016 12 12 = 14 ft2