"Published in Newark, California, USA"
A contractor agrees to build a dam, 180 ft. long and 20 ft. high, 12 ft. wide at the bottom and 8 ft. wide at the top, for $9.75 a cubic yard. Find his profit if his costs were $10,000.
Solution:
To illustrate the problem, it is better to draw the figure as follows
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| Photo by Math Principles in Everyday Life |
The area of the base which is a trapezoid is
The volume of a dam which is a trapezoid prism is
The volume of a dam in cubic yards is
The labor cost of building a dam is
Therefore, the contractor's profit in building a dam is
