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274
Solving Area Equations
Reteach
You can use area formulas to find missing dimensions in figures.
The formula for area of a parallelogram is A = bh.
The formula for area of a trapezoid is A =
1
2
h(b
1
+ b
2
).
The formula for area of a rhombus is A =
1
2
d
1
d
2
.
The formula for area of a triangle is A =
1
2
bh.
Suppose you know the area of a triangle is 28 square feet. You also
know the length of the base of the triangle is 7 feet. What is the height of
the triangle?
Use the formula for area of a triangle. A =
1
2
bh
Substitute known values. 28 =
1
2
(7)h
Multiply both sides by 2. 56 = 7h
Divide both sides by 7. 8 = h
The height of the triangle is 8 feet.
Solve.
1. The area of a parallelogram is 150 square meters. The height of the
parallelogram is 15 meters. What is the length of the parallelogram?
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2. The length of one diagonal of a rhombus is 8 cm. The area of the
rhombus is 72 square centimeters. What is the length of the other
diagonal of the rhombus?
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3. The area of a triangle is 32 square inches. The height of the triangle is
8 inches. What is the length of the base of the triangle?
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4. The area of a rectangle is 34 square yards. The length of the rectangle
is 17 yards. What is the width of the rectangle?
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5. The area of a trapezoid is 39 square millimeters. The height of the
trapezoid is 6 millimeters. One of the base lengths of the trapezoid is
5 millimeters. What is the length of the other base of the trapezoid?
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LESSON
13-3