Question

7. The length of a rectangle is 4 cm more than the
breadth, should the length and breadth be increased
by 3 cm, the area increase by 81 square cm. What is
the length and breadth of the rectangle?
(a) 15, 10 cm
(b) 14, 10 cm
(c) 10,5 cm
(d) None of these​

Answer 1

Answer:

$option \: (b) \: is \: correct$

Step-by-step explanation:

$l = 4 \: + b \\ lb + 81 = (l + 3)( b+ 3) \\ lb + 81= lb + 3l + 3b + 9 \\ 3l + 3b + 9 - 81= 0 \\ \\ or \: \: l + b + 3 - 27= 0 \\ \\ \\ \\ \\ sovling \: above \: equations \\ \\ 4 + b + b + 3 - 27 = 0 \\ \\ 2b - 20 = 0 \\ 2b = 20 \\ b = 10 \: cm \\l = 4 + 10 = 14 \: cm \\ \\ therefore \: (b) \: is \: correct.$