Math CentralQuandaries & Queries


Question from Hailey, a student:

The area of a triangle is 77ft2. if the base is 11ft. how tall is the height?

Hi Hailey,

You know that the area $A$ of a triangle is given by

\[A = \frac12 \times b \times h\]

where $b$ is the length of the base and $h$ is the height. Fill in the values you know, $A = 77$ square feet and $b = 11$ feet.

This results in an equation where the only unknown is the height $h.$ Solve this equation for $h.$ If you have difficulty solving for $h$ have a look at these three somewhat similar examples. 1, 2 and 3.

Once you have determined the value of $h$ you can check your answer. Us the formula

\[A = \frac12 \times b \times h\]

with $b = 11$ feet and $h$ the value you obtained to see if you get an area of $77$ square feet.


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