GRE考试

【单选题】





网考网参考答案：A
网考网解析：
If the average of the three digits is 2, the sum of the digits is 6. The simplest thing is to list them. If there are only a few, list them all; if it seems that there will be too many to list, look for a pattern. The list starts this way: 105, 114, 123, 132, 141, 150, so there are6 of them in the 100s. Continue: 204, 213, 222, 23I, 240. There are 5 in the 200s. You can conclude, correctly, that there are 4 in the 300s, 3 in the 400s, 2 in the 500s, and 1 in the 600s. So, the total is 6 + 5 +4 + 3 + 2 + 1 = 21. If you don’t spot the pattern, just continue the list: 303, 312,…, 501,510, 600. document.getElementById("warp").style.display="none"; document.getElementById("content").style.display="block"; 查看试题解析出处>>