Please allow me to use area of circle as = πd^2 / 4
Therefore πd^2 / 4 = 49π Cancel out π from both sides.
d^2 / 4 = 49 Cross Multiply
d^2 = 4*49
d^2 = 196 Take the square root of both sides
d = √196 Use your calculator
d = 14
Hence, diameter of the circle is 14 units.
Cheers.