Qstnid -B-4- The Area Of A Small Rectangular Plot Is 84 M2. If The Difference Between Its Length And The Breadth Is 5 M; Find Its Perimeter. - 20: Area Of Trapezium And A Polygon Class 8 Maths - Icse-viii-mathematics

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ICSE-VIII-Mathematics

20: Area of Trapezium and a Polygon Class 8 Maths

with Solutions - page 3

Qstn# B-4 Prvs-Qstn Next-Qstn

#4
The area of a small rectangular plot is 84 m2. If the difference between its length and the breadth is 5 m; find its perimeter.
Ans : Area of a rectangular plot = 84 m²
Let breadth = x m
Then length = (x + 5) m
Area = l × bx(x + 5) = 84
⇒ x ²+ 5x - 84 = 0
⇒ x² + 12x - 7x - 84 = 0
⇒ x(x + 12) - 7(x + 12) = 0
⇒ (x + 12) (x - 7) = 0
Either x + 12 = 0, then x = -12 which is not possible being negative
or, x - 7 = 0, then x = 7
Length = x + 5 = 7 + 5 = 12m
and breadth = x = 7 m
Perimeter = 2(l + b) = 2(12 + 7) = 2 × 19 m = 38 m