GRE考试

【单选题】



网考网参考答案：C
网考网解析：
The simplest solution is to realize that there is one palindrome between 100 and 109 (101), one between 390 and 399 (393), one between 880 and 889 (888), and in general, one out of every 10 numbers. So the probability is [*] The answer is (C). **The more direct solution is to count the number of palindromes. Either systematically make a list and notice that there are 10 of them between 100 and 199, and 10 in each of the hundreds from the 100s to the 900s, for a total of 90; or use the counting principle: the first digit can be chosen in any of 9 ways, the second in any of 10 ways, and the third, since it must match the first, can be chosen in only 1 way (9 × 10 × 1 = 90). Since there are 900 three-digit numbers, the probability is [*] document.getElementById("warp").style.display="none"; document.getElementById("content").style.display="block"; 查看试题解析出处>>