Answer:

Step-by-step explanation:
If two values are inversely proportional, their product must be maintained. That way, if one value goes up, the other goes down by the same extent.
Therefore, if
and
vary inversely, their product will be the same for all values of
and
.
Let
and
as given in the problem. Substitute values:

Hence, the maintained product is
.
Thus, we have the following equation:

Substitute
to find the value of
when
:

You need to first set up the equation:
It would look like 90 divided by 360 multiplied by the given
circumference which is 72 cm.
So 90 / 360 x 72
Simply the fraction above, it will give us:
¼ x 72
So the answer would be 18 cm that is the length of DE (minor
arc)
10 windows : divide 40/5=8
Then divide 80/8 =10