Calculate the areas of circles with the following diameters π as 22/7. a) 14 cm, b) 7 cm, c) 42 cm, d) 21 cm

$$r = \frac{1.4 \text{ cm}}{2} = 0.7 \text{ cm}$$ $$A = \frac{22}{7} \times (0.7 \text{ cm})^2 = \frac{22}{7} \times 0.49 \text{ cm}^2$$

$$A = 22 \times \frac{0.49}{7} \text{ cm}^2 = 22 \times 0.07 \text{ cm}^2$$ $$A = 1.54 \text{ cm}^2$$

The area of the circle is $\boxed{\text{1.54 cm}^2}$.

$$r = \frac{7 \text{ cm}}{2} = 3.5 \text{ cm}$$ $$A = \frac{22}{7} \times (3.5 \text{ cm})^2 = \frac{22}{7} \times 12.25 \text{ cm}^2$$

$$A = 22 \times \frac{12.25}{7} \text{ cm}^2 = 22 \times 1.75 \text{ cm}^2$$ $$A = 38.5 \text{ cm}^2$$

The area of the circle is $\boxed{\text{38.5 cm}^2}$.

$$r = \frac{42 \text{ cm}}{2} = 21 \text{ cm}$$ $$A = \frac{22}{7} \times (21 \text{ cm})^2 = \frac{22}{7} \times 441 \text{ cm}^2$$

$$A = 22 \times \frac{441}{7} \text{ cm}^2 = 22 \times 63 \text{ cm}^2$$ $$A = 1386 \text{ cm}^2$$

The area of the circle is $\boxed{\text{1386 cm}^2}$.

$$r = \frac{21 \text{ cm}}{2} = 10.5 \text{ cm}$$ $$A = \frac{22}{7} \times (10.5 \text{ cm})^2 = \frac{22}{7} \times 110.25 \text{ cm}^2$$

$$A = 22 \times \frac{110.25}{7} \text{ cm}^2 = 22 \times 15.75 \text{ cm}^2$$ $$A = 346.5 \text{ cm}^2$$

The area of the circle is $\boxed{\text{346.5 cm}^2}$.