Scientific notation is a way of writing very large and very small numbers. We are asked the product of 1632 (4 significant figures) * 4.0*10^4 (2 significant figures) = 65 280 000 or 6.528*10^7. The rule says that we need to follow the number of significant figures of the factor with the least significant figures, in this case 4.0*10^4 (2 significant figures) . The final answer will then be 6.5*10^7.
