Calculate the percentage discount and the area of a circular table top.

The discount is the marked price minus the selling price.

$$Discount = \text{sh. } 600 - \text{sh. } 570 = \text{sh. } 30$$

The percentage discount is the discount amount divided by the marked price, multiplied by 100%.

$$Percentage \text{ } Discount = \frac{30}{600} \times 100\%$$ $$Percentage \text{ } Discount = \frac{1}{20} \times 100\%$$ $$Percentage \text{ } Discount = 5\%$$

The percentage discount was $\boxed{5\%}$.

27)

The diameter is given as $90 \text{ cm}$. The radius is half of the diameter.

$$r = \frac{diameter}{2} = \frac{90 \text{ cm}}{2} = 45 \text{ cm}$$

The area of a circle is given by the formula $A = \pi r^2$. Use $\pi = 3.142$.

$$A = 3.142 \times (45 \text{ cm})^2$$ $$A = 3.142 \times 2025 \text{ cm}^2$$ $$A = 6361.05 \text{ cm}^2$$

The area of the table top is $\boxed{6361.05 \text{ cm}^2}$.