Cannot understand the sum .please explain it

Cannot understand the sum .please explain it (8 + Jitj)y units. Perimeter of A AEC : perimeter of trap. ABEC (4 + ) : (8 + Example 17 II' the length ofa rectangle is increased by 10 cm and the breadth by 5 Cln, the area is unaltered. If the length is chq Teased by and Increased by 4 cm, even then the area is unaltered. Find the ('f the Solution. Let the length and the breadth Of the rectangle be x cm and y cm respectively, then its area = xy cm . According to the first condition of the question, when length is increased by 10 cm and breadth decreased by 5 cm, area of the rectangle remains unaltered. (x + 10) (y — 5) = xy xy —5x + I Oy — 50 = xy -5x+ loy -50 = o x — 2Y+ 10 = O According to the second condition of the question, we get (x — 5) (y + 4) = xy xy +4x — 5y — 20 = xy 4x-5y-20=O Multiplying (i) by 4, we get Subtracting (iii) from (it), we get 3y — 60 = 0 3y = 60 y = 20. From we get x-2x20+10=o 10=0 —x = 30. Hence the length of the rectangle = 30 cm and its breadth = 20 cm. plenf The side of a square exceeds the side of another square by 3_cm and the s of the areas of the two squares is 549 cm2. Find the perimeters of the squares.

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