问题
单项选择题
A child withdraws from his piggy bank 10% of the original sum in the bank. If he must add 90￠ to bring the amount in the bank back up to the original sum, what was the original sum in the bank ？（）
A.$1.00
B.$1.90
C.$8.10
D.$9.00
E.$9.90
答案
参考答案：D