Bunuel

If the width of the rectangle above is increased by 50 percent and the length remains the same, by what percent will the area of the rectangle be increased?
(A) 50%
(B) 100%
(C) 150°
(D) 200°
(E) cannot be determined from the information given
Attachment:
2017-10-04_1124.png
Assume x = 10 and y = 4. (Choose easily multiplied numbers. For y, choose a number that, when multiplied by 1.5 or \(\frac{3}{2}\), yields an integer.)
Original area = (L * W) = 40
Width increases by 50 percent. New width is \((4)*\frac{3}{2} = 6\)
New area = (L * W) = 10 * 6 = 60
Percent increase in area =
\(\frac{New - Old}{Old} * 100\)
\(\frac{60 - 40}{40} =(\frac{20}{40}) * 100\) = 50 percent
ANSWER A
Algebra might be faster (not by much). Typically, both lengths increase. There are more multipliers, often squared. Here, just one length increases:
Original area = (y)(x)
New area = (1.5y)(x)
Percent increase:
\(\frac{1.5yx - 1yx}{yx} =\\
\frac{.5}{1} * 100\) = 50 percent