30. Decrease $\$ 1000$ by $10 \%$. Increase the result by $10 \%$. What do you discover?

Step 1 ：First, we need to decrease $1000 by $10 \%$. This can be done by multiplying $1000 by $0.9 (since $10 \%$ decrease means we are left with $90 \%$ of the original amount).

Step 2 ：Next, we need to increase the result by $10 \%$. This can be done by multiplying the result by $1.1 (since $10 \%$ increase means we are adding $10 \%$ to the original amount).

Step 3 ：We will then compare the final result with the original amount to see what we discover.

Step 4 ：The final amount is less than the original amount. This is because a percentage decrease followed by the same percentage increase does not result in the original amount. The percentage increase is applied to the decreased amount, not the original amount, resulting in a smaller final amount.

Step 5 ：Final Answer: The final amount is \(\boxed{990}\), which is less than the original amount of \(\boxed{1000}\).