Question
Find the long base $ a $ of a trapezoid if short base $b = 3\, \text{cm}$, height $h = 40\, \text{cm}$ and area $A = 260\, \text{cm}$.
Answer
$10$
Explanation
To find long base $ a $ use formula:
$$ A = \frac{ (a + b) \cdot h}{ 2 }$$After substituting $ A = 260 $ , $ b = 3 $ and $ h = 40 $ we have:
$$ 260\, \text{cm} = \frac{ (a + 3\, \text{cm}) \cdot 40\, \text{cm}}{ 2 }$$$$ 260\, \text{cm} \cdot 2 = (a + 3\, \text{cm}) \cdot 40\, \text{cm} $$$$ 520\, \text{cm} = (a + 3\, \text{cm}) \cdot 40\, \text{cm} $$$$ a + 3\, \text{cm} = \frac{ 520\, \text{cm} }{ 40\, \text{cm} } $$$$ a + 3\, \text{cm} = 13 $$$$ a = 13 - 3\, \text{cm} $$$$ a = 10 $$This page was created using
Trapezoid Calculator