Find the perimeter of rectangle whose length is 40 cm and diagonal is 41 cm.
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Solution
In right △ADC, by Pythagoras theorem, AC2=AD2+CD2 412=402+CD2 CD2=412−402=(41−40)(41+40)=81 CD=9 cm Thus, the breadth CD=9 cm Perimeter = 2(l+b)=2×(40+9)=98 cm