2011 UPPER PRIMARY DIVISION FIRST ROUND SOLUTION
1. 2011－1022=989.
Answer：（C）
2. The last lesson starts at 2:30 p.m. As each lesson lasts for forty five minutes, the last lesson ends at 3:15 p.m. At this time, the minute hand points at three and the hour hand points between three and four in the clock. Thus the angle between the hour hand and minute hand is larger than 0° and smaller than 90°.
Answer：（C）
3. The area of figure A, B, C, D and E are 8, 10, 9, 7, 9 respectively.
Answer：（B）
4. The area of the shaded region with respect to toal area in figure A, B, C, D, E are3
5, 4 8 , 3
8, 6 8 , 20
25. Among them, 20
25is larger than3 4 .
Answer：（E）
5. The successive two pages illustrate that those two page numbers are consecutive natural numbers. As the sum of that two consecutive natural numbers is 345, The two numbers are (345-1)÷2=172 and 172+1=173 respectively. Therefore , the story starts at page172.
Answer：（D）
6. All alphabets are arranged in periodic order, with every five alphabets forms a period. When 2011 is divided by 5, the remainder equals to 1, it follows that the 2011th alphabet equal to the first alphabet, which is M. Hence A.
Answer：（A）
7. 3 3
3 3
2 2
× = + . Answer：（B）
【Remarks】Generally, if a+b=ab, then a, b satisfy (a−1)(b− =1) 1.
8. The area of the large triangle equals to the area of 16 small shaded triangles.
Since there are 6 small shaded triangles, the ratio is 6 3
16 =8=37.5 %.
Answer：（D）
9. When counts from left to right¸ Mickey is the thirteenth student. He has
seventeen classmates in his right hand side. When Mickey counts from right to left, he will be the eighteenth student.
Answer：（A）
10. Among the 20 balls, there is only one ball marked with 11. Ten balls with even number printed. Four balls with last unit number equals to 5, 6, 7 and 8. There are 11 balls containing the digit “1” and 9 balls with one digit number printed.
Answer：（D）
11. The pattern of the graphic follows the rule that each four of them forms a period.
Since 2011÷4=502……3, it equals to the third figure, hence A.
Answer：（A）
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Using the above process, we can deduce the following：
At the beginning of the game, there are 4 different combinations of 6 counters.
Answer：004
25. Note that every line has 5 interchange stations. When traveling on one line, at most two changes are made. Thus, Mickey needs to ride at least 3 times on each line. For the line that come-across his home, he needs to ride four times. (Since it starts and ends in the station near his home, and there will not be change).As a result, Mickey needs to ride at least
3 5× + =4 19 times. In other words, he needs to make 18 changes. Refer to the figure on the right, it shows six lines A, B, C, D, E, F and interchange stations 1 to 15.
Mickey starts at H, he can take the following route, which included 18 changes to go back to station H.
H→15→4→1→9→14→3→2→12→5→4
→13→10→6→8→11→10→7→9→H
Answer：018
After operation ● ●
Before operation ○ ●
or
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E F C D
B A
H
E D C B 1 2 3 4 5 A
6 7 8 9 10 11 12
13 14 15
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The first operation The second operation
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