Two concentric circles form a ring. The inner and outer circumferences of the ring are 22 cm and 44 cm, respectively. The width of the ring is: (take $$\pi = \frac{22}{7}$$)

Let the radius of inner and outer circles are $$r_1$$ and $$r_2$$ respectively.

Circumference of inner circle = 22 cm

$$\Rightarrow$$  $$2\pi\ r_1=22$$

$$\Rightarrow$$  $$2\times\frac{22}{7}\times\ r_1=22$$

$$\Rightarrow$$  $$\ r_1=3.5$$ cm

Circumference of outer circle = 44 cm

$$\Rightarrow$$  $$2\pi\ r_2=44$$

$$\Rightarrow$$  $$2\times\frac{22}{7}\times r_2=44$$

$$\Rightarrow$$  $$r_2=7$$ cm

$$\therefore\ $$Width of the ring = $$r_2-r_1\ $$ = 7 - 3.5 = 3.5 cm

Hence, the correct answer is Option D