Question

How do you work out the length of radius and diameter of these two circles?

Answer 1

So for the first one what you did was wrong as in wrong formula.
Radius is 5cm as it is given and diameter is double the radius which is 10.
So r=5
And D=10.

For the second one the diameter is 16cm as it is given and radius is half the diameter,so half of 16 is 8cm right?
So r=8
And D=16