Difference between revisions of "1989 AJHSME Problems/Problem 15"
5849206328x (talk | contribs) (New page: ==Problem== The area of the shaded region <math>\text{BEDC}</math> in parallelogram <math>\text{ABCD}</math> is <asy> unitsize(10); pair A,B,C,D,E; A=origin; B=(4,8); C=(14,8); D...) |
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<math>\text{(A)}\ 24 \qquad \text{(B)}\ 48 \qquad \text{(C)}\ 60 \qquad \text{(D)}\ 64 \qquad \text{(E)}\ 80</math> | <math>\text{(A)}\ 24 \qquad \text{(B)}\ 48 \qquad \text{(C)}\ 60 \qquad \text{(D)}\ 64 \qquad \text{(E)}\ 80</math> | ||
− | ==Solution== | + | ==Solution 1== |
− | Let <math> | + | Let <math>[ABC]</math> denote the area of figure <math>ABC</math>. |
− | Clearly, <math> | + | Clearly, <math>[BEDC]=[ABCD]-[ABE]</math>. Using basic area formulas, |
− | |||
− | |||
− | + | <center><math>[ABCD]=(BC)(BE)=80</math></center> | |
− | Finally, we have <math> | + | <center><math>[ABE]=(BE)(AE)/2 = 4(AE)</math></center> |
+ | |||
+ | Since <math>AE+ED=BC=10</math> and <math>ED=6</math>, <math>AE=4</math> and the area of <math>\triangle ABE</math> is <math>4(4)=16</math>. | ||
+ | |||
+ | Finally, we have <math>[BEDC]=80-16=64\rightarrow \boxed{\text{D}}</math> | ||
+ | |||
+ | ==Solution 2== | ||
+ | |||
+ | Notice that <math>BEDC</math> is a trapezoid. Therefore its area is <cmath>8\left(\frac{6+10}{2}\right)=8\left(\frac{16}{2}\right)=8(8)=64\Rightarrow \mathrm{(D)}</cmath> | ||
==See Also== | ==See Also== | ||
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{{AJHSME box|year=1989|num-b=14|num-a=16}} | {{AJHSME box|year=1989|num-b=14|num-a=16}} | ||
[[Category:Introductory Geometry Problems]] | [[Category:Introductory Geometry Problems]] | ||
+ | {{MAA Notice}} |
Latest revision as of 23:03, 4 July 2013
Contents
Problem
The area of the shaded region in parallelogram is
Solution 1
Let denote the area of figure .
Clearly, . Using basic area formulas,
Since and , and the area of is .
Finally, we have
Solution 2
Notice that is a trapezoid. Therefore its area is
See Also
1989 AJHSME (Problems • Answer Key • Resources) | ||
Preceded by Problem 14 |
Followed by Problem 16 | |
1 • 2 • 3 • 4 • 5 • 6 • 7 • 8 • 9 • 10 • 11 • 12 • 13 • 14 • 15 • 16 • 17 • 18 • 19 • 20 • 21 • 22 • 23 • 24 • 25 | ||
All AJHSME/AMC 8 Problems and Solutions |
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