The figure below is a diagram of a trapezoidal table that needs to be stained. Each can of stain will cover 50 square inches.
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Note that there are some useless information here. But all you need to know is that the area of a trapezium is the average of the 2 parallel bases multiplied by the height.
Area = (32 + 24) / 2 * 9 = 252
Since 5 cans of stain can only cover an area of 250, you will need 6 cans of stain.