Question

triangles & rectangles
to find the area of a triangle, multiply the base and the height together. then, divide product by 2. remember, the height is perpendicular to the base.
there are two ways to write the formula to find the area of a triangle:
$a = \frac{1}{2}bh$ or $a = \frac{bh}{2}$
example problem (how to show your steps):
find the area of the given triangle:
example of how to show your steps:

1. write the formula $a = \frac{1}{2}bh$ or $a = \frac{bh}{2}$
2. plug in the numbers $a = \frac{1}{2}\bullet 20 \bullet 8$ or $a = \frac{20 \bullet 8}{2}$
3. do the math $a = 10 \bullet 8$ $a = 80\\ cm^2$ or $a = \frac{160}{2}$ $a = 80\\ cm^2$

directions: find the area of each of the following triangles or rectangles.
show your work like the example above.
1.
2.
3.

Explanation:

Problem 1 (Rectangle)

Step1: Recall rectangle area formula

$A = l \times w$

Step2: Substitute given values

$A = 12\frac{3}{4} \times 4$

Step3: Convert mixed number to fraction

$12\frac{3}{4} = \frac{51}{4}$, so $A = \frac{51}{4} \times 4$

Step4: Calculate the product

$A = 51$

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Problem 2 (Triangle)

Step1: Recall triangle area formula

$A = \frac{1}{2}bh$

Step2: Substitute given values

$A = \frac{1}{2} \times 15.6 \times 6$

Step3: Multiply base and height first

$15.6 \times 6 = 93.6$

Step4: Divide product by 2

$A = \frac{93.6}{2} = 46.8$

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Problem 3 (Triangle)

Step1: Recall triangle area formula

$A = \frac{1}{2}bh$

Step2: Substitute given values

$A = \frac{1}{2} \times 3.6 \times 2.4$

Step3: Multiply base and height first

$3.6 \times 2.4 = 8.64$

Step4: Divide product by 2

$A = \frac{8.64}{2} = 4.32$

Answer:

1. $51$ in²
2. $46.8$ cm²
3. $4.32$ cm²