Calculate the percentage discount and the area of a circular table top with a diameter of 90 cm, using pi = 3.142.

The discount is the difference between the marked price and the selling price.

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

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

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

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

27)

The diameter is $90 \text{ cm}$. The radius ($r$) is half of the diameter.

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

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

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

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