Question

下列哪个数最大？

Which of the following numbers is the largest?

$0.99$

$0.9099$

$0.9$

$0.909$

$0.9009$

知识点：小数位值

可以在小数末尾补零，把它们写成相同位数再比较

Give every number the same number of decimal places by appending zeros

从左向右逐位比较；百分位上的数字决定这些以 $0.9$ 开头的数的大小

Compare digit by digit from the left; the hundredths place decides between the leading $0.9$ numbers

把这些数都写成四位小数： $0.9900$ 、 $0.9099$ 、 $0.9000$ 、 $0.9090$ 、 $0.9009$ 。

从左向右比较可知， $0.9900$ 的百分位数字最大，所以 $0.99$ 最大。

所以正确答案是 A。

Write each number with four decimal places: $0.9900,$ $0.9099,$ $0.9000,$ $0.9090,$ $0.9009.$

Comparing from the left, $0.9900$ has the largest hundredths digit, so $0.99$ is the largest.

Thus, the correct answer is A .