Two adjacent sides of a parallelogram are 21 cms and 20 cms The diagonal joining the endpoints of th...........

Quantitative Aptitude (CGL) Mensuration 2D

Two adjacent sides of a parallelogram are 21 cms and 20 cms. The diagonal joining the endpoints of these two sides is 29 cms. The area of the parallelogram (in sq. cms) is

240

120

210

420

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Explanation:

Area of Rectangle ABCD = 2 * ( Area of triangle ABC);
Hence, The area of triangle ABC = √s(s-a)(s-b)(s-c); where s = (a + b + c)/2;
s = (20 + 21 + 29)/2 = 35;
The area of triangle ABC = √35(35-20)(35-21)(35-29) = √35*15*14* 6 = 7*5*3*2 = 210 sq. cms.
Hence, the area of parallelogram= 210*2 = 420 sq. cms.