The regular price for a bicycle is $\$ 320$. The bicycle is on sale for $20 \%$ off. The regular price for a helmet is $\$ 80$. The helmet is on sale for $10 \%$ off. If Sandra bought both items on sale, what is her percentage savings on the total purchase?
(A) $18 \%$
(B) $12 \%$
(C) $15 \%$
(D) $19 \%$
(E) $22.5 \%$
Since the regular price for the bicycle is $\$ 320$ and the savings are $20 \%$, then the amount of money that Sandra saves on the bicycle is $\$ 320 \times 20 \%=\$ 320 \times 0.2=\$ 64$.

Since the regular price for the helmet is $\$ 80$ and the savings are $10 \%$, then the amount of money that Sandra saves on the helmet is $\$ 80 \times 10 \%=\$ 80 \times 0.1=\$ 8$.

The total of the original prices for the bicycle and helmet is $\$ 320+\$ 80=\$ 400$.

Sandra's total savings are $\$ 64+\$ 8=\$ 72$.

Therefore, her total percentage savings is $\frac{\$ 72}{\$ 400} \times 100 \%=\frac{72}{4} \times 1 \%=18 \%$.

ANSWER: (A)