单选题
【正确答案】
B
【答案解析】The area of the large square is S2, and the area of the small square is s2, so the area of the shaded region is S2 -s2. Since the shaded region and the unshaded region have the same area,
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which is less than 1.5 Column B is greater.
[*]
which is less than 1.5 Column B is greater.
【正确答案】
A
【答案解析】You do not need to add the lengths of the steps. Together, all the horizontal steps are equal to the bottom, and all the vertical risers are equal to the left side. The sum of the left side, 5 feet 4 inches, or 64 inches, and the bottom, 9 feet 2 inches, or 110 inches, is half the perimeter. The perimeter is 2(64 + 110) = 2(174) = 348 inches. Column A is greater.
【正确答案】
A
【答案解析】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.
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.