Answer:
C. 3.4 feet
Step-by-step explanation:
Let, the amount of increase be 'x' feet.
As, the length and width of the garden are 20 ft and 12 ft respectively.
It is given that the area of the new garden is 360 ft²
Since, the length and width are increased by 'x'.
The new length and width are (x+20) ft and (x+12) ft respectively.
So, we get,
New area, = length × breadth = (x+20) × (x+12)
i.e. 360 =
i.e.
i.e. (x+35.4)(x-3.4)=0
i.e. x = -35.4 and x= 3.4
Since, the value of x cannot be negative.
Thus, x = 3.4 feet.