Answer:
When multiplying numbers, the number of significant figures in the product is determined by the number of significant figures in the least precise factor.
In this case, the least precise factor is 9.0 cm, which has two significant figures. Therefore, the product should be rounded to two significant figures.
The product of 18.0 cm and 9.0 cm is 162.0 cm^2. Rounded to two significant figures, the answer is 160 cm^2.
Therefore, there are two significant figures in the answer, which is determined by the least precise factor (9.0 cm).