In: Advanced Math
A concrete walk 3 feet wide is placed around the outside of a circular pond with diameter 15 feet.
What is the total cost of the walk if the cost per square foot is $1.31
We have to figure out the area of the feet wide walk. Lets
look at the picture. The walk is the green area.
The diameter of the pond is given to be
feet
and hence the radius is
feet. The walk is
feet wide and hence the
outside radius is,
. Then the area covered by the walk is the difference between the
areas of the larger circle and the inner circle. Now we know that
the area of a circle of radius
is given by
. Hence the
area of the walk is
square feet.
Now cost for each square foot is given to be . Hence
the total cost is,
dollars. This is approximately equals,
.