AMC 8 Daily Practice Round 2

Complete problem set with solutions and individual problem pages

Problem 1 Easy

Sara had ten dollars for lunch. She bought a hamburger, a salad, and a cup of apple juice for 3.48, 2.2, and 1.42 dollars, respectively. How many dollars did she have after lunch?

  • A.

    2.78

  • B.

    2.8

  • C.

    2.9

  • D.

    2.98

  • E.

    3.1

Answer:C

3.48+2.2+1.42=3.48+1.42+2.2=4.9+2.2=7.1

10-7.1=2.9

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Problem 2 Easy

As the figure shown, this is a net of a cube. Fill appropriate numbers in three squares A, B, and C, so that the sum of two numbers on the opposite faces after folding into a cube is 0. Then the three numbers filled in the squares A, B, and C are            , respectively.

  • A.

    1,-2,0

  • B.

    0,-2,1

  • C.

    -2,0,1

  • D.

    -2,1,0

  • E.

    0, 1, -2

Answer:A

Pay attention: the sum of opposite number has to be 0. From the net we can get the answer \text{A}.

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Problem 3 Easy

In a class of 52 students, students like to play either basketball, or badminton, or both. If there are 30 students who like to play basketball and 36 students who like to play badminton, how many students like to play both?

  • A.

    14

  • B.

    16

  • C.

    18

  • D.

    20

  • E.

    22

Answer:A

30+36-52=14

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Problem 4 Easy

There are 1000 students in the school, and 100 of them are randomly chosen for sampling. The table below shows the range of heights (\text{cm}) of the 100 students. Find the range where the median lies.

Range of Height(\text{cm})Frequency
120\leqslant h\lt1308
130\leqslant h\lt14016
140\leqslant h\lt15025
150\leqslant h\lt16030
160\leqslant h\lt17021
  • A.

    120\leqslant h\lt130

  • B.

    130\leqslant h\lt140

  • C.

    140\leqslant h\lt150

  • D.

    150\leqslant h\lt160

  • E.

    160\leqslant h\lt170

Answer:D

According to the definition of median, we need to find the range which the 50th student and 51st student lie. The answer is D.

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Problem 5 Easy

The thousands digit of a four-digit number is 4 less than the ones digit. Then reverse all the digits of the four-digit number to get a new number. Then we subtract the original number from the new four-digit number. What is the ones digit of the result after subtraction?

  • A.

    3

  • B.

    4

  • C.

    5

  • D.

    6

  • E.

    7

Answer:D

Method1: Let the thousands, hundreds, tens, and ones digits of the original four-digit number be a, b, c, and d respectively. We are given that a=d-4. The original four-digit number is equal to 1000a+100b+10c+d=1001d+100b+10c-4000. The thousands, hundreds, tens and ones digits of the reversed four-digit number are d, c, b, and a, respectively. This number is equal to 1000d+100c+10b+a=1001d+100c+10b-4. Subtracting the original expression from the new one, we get\left( 1001d+100b+10c-4000 \right)-\left( 1001d+100c+10b-4 \right)=90c-90b+3996. Thus, the ones digit in the final result is 6.

Method2:The result must hold for any four-digit number with thousands digit being 4 less than the ones digit. 1025 is such a number. Evaluating we get 5201-1025=4176. Thus, the ones digit in the final result is 6.

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