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Question
The area of a rectangle of length 21 cm and diagonal 29 cm is __________
Options
609 cm2
580 cm2
420 cm2
210 cm2
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Solution
420 cm2
Explanation;
Hint:
length = 21 cm
diagonal = 29 cm
By the converse of Pythagoras theorem,
AB2 + BC2 = AC2
212 + x2 = 292
x2 = 841 – 441
400 = 202
x = 20 cm
Now area of the rectangle = length × breadth.
i.e AB × BC
= 21 cm × 20 cm
= 420 cm2
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