"Published in Newark, California, USA"
In 1964, Mr. Tambasen bought a rectangular lot in Bacolod City for ₱ 18,000 and spent ₱ 1,000 for building a wall around it. If the cost per square meter of the lot is ₱ 30 and the cost per linear meter of the wall is ₱ 10, find the dimensions of the lot.
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 |
Let x = be the length of a rectangular lot
y = be the width of a rectangular lot
The area of a rectangular lot is 
.
.
The perimeter of a rectangular lot is 
.
.The first working equation which is the cost of a rectangular lot is
The second working equation which is the total cost of building a wall around the rectangular lot is
Substitute the value of y to the first working equation, we have
By using the completing the square method, the value of x which is the length of a rectangular lot is
If you choose the positive sign, the value of x is
and the value of y which is the width of a rectangular lot is
If you choose the negative sign, the value of x is
and the value of y which is the width of a rectangular lot is
Therefore, the dimensions of a rectangular lot are 30 m by 20 m.