If the perimeter of a rectangle and a square is equal to 80 cm and the difference of their areas is 100 sq.cm. the sides of the rectangle are :
Side of the square = `80/4` cm = 20 cm.
2(l + b) = 80
`rArr l + b = 40`, now (20 x 20) - lb = 100
`hArr lb = 300`
(l - b) = `sqrt((l + b)^2 - 4lb)` = `sqrt((40 xx 40) - (4 xx 300))` = `sqrt(400)` = 20.
Now , l + b = 40 and l - b = 20
`rArr l = 30 and b = 10`
`:.` sides of the rectangle are 30 cm and 10 cm.
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