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An isosceles trapezoid with a perimeter of 42 inches. Each of the congruent non parallel sides is 5 inches long, and the trapezoid is 3 inches tall. How long are the two parallel sides?

A. 10 in, 22 in
B. 16 in, 16 in
C. 10 in, 16 in
D. 12 in, 20 in

User PCheese
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1 Answer

4 votes

Answer:

Longer - 20 in and Shorter - 12 in

Explanation:

We know that when we subtract the shorter side from longer we get two cuts named x:

2 x = a - b => a - b = 2 x

One of this section ( x ) with height ( h ) and lateral (congruent non parallel) side ( c ) make right triangle, from which we get:

x² = c² - h² and c = 5 in, h = 3 in

x² = 5² - 3² = 25 - 9 = 16 => x = √16 = 4 => x = 4 in

Now we will replace x = 4 in the equation a - b = 2 · 4 = 8 and get first equation of the system.

a - b = 8

We also know that the formula for calculating perimeter is:

P = a + b + 2 c where P = 42 in and c = 5 in

a + b = 42 - 2 · 5 = 42 - 10 = 32

Now we get the second equation of the system:

a + b = 32

a - b = 8

When we add first equation to the second we get:

2 a = 40 => a = 40 / 2 = 20 => a = 20 in

When we replace a = 20 in the first equation we get:

20 + b = 32 => b = 32 - 20 = 12 => b = 12 in

God with you!!!

User Nazimboudeffa
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