How do you work out
4/5 of 65

You divide 65 by 5 and then multiply that by 4 
65/5=13
13 times 4 equals 52 
52 is the answer

Another way that my teacher to taught me is to think of the word "of" as a multiplication sign, so it'd be
4/5 x 65.

That would be 4/5 x 65/1.

4x65=260
Don't forget about the denominator 5 though...

So that would be 260/5.

That is 52.

The answer is "a"radius = 12.7 unitsdiameter = radius × 212.7 units × 2 = 25.4 units