The circumference of the two circles is 77 cm and 154 cm respectively. What is the difference between their radii?

12.25 cm

Let the radius of the first circle be r1 and radius of second circle r2.

Then, we have

2\(\Pi \)r1 = 77   ..(1)

2\(\Pi \)r2 = 154  ..(2)

Dividing equation (2) by (1),

\(\frac{r2}{r1}\) = \(\frac{154}{77}\)

\(\frac{r2}{r1}\) = 2

r2 = 2r1

Now, the difference between their radiiis

r2 - r1 = 2r1 - r1 = r1

From equation (1), we have

2\(\Pi \)r1 = 77

r1 = \(\frac{77}{2(3.14)}\)

r1 = 12.25 cm (approx)

Therefore, the difference between their radii is 12.25 cm.