AMC 8 Daily Practice - Calculation Tricks by Grouping

Complete problem set with solutions and individual problem pages

Problem 1 Easy

What is the value of (7 + 8 + 9) - 7 + (7 + 8 + 9) - 8 + (7 + 8 + 9) - 9?

  • A.

    -24

  • B.

    24

  • C.

    48

  • D.

    72

  • E.

    96

Answer:C

Through observation, we notice that the expression (7 + 8 + 9) appears repeatedly in the original formula.

The expression can be rewritten as: (7 + 8 + 9) - 7 + (7 + 8 + 9) - 8 + (7 + 8 + 9) - 9 = (7 + 8 + 9) + (7 + 8 + 9) + (7 + 8 + 9) - 7 - 8 - 9 = 3 \times (7 + 8 + 9) - (7 + 8 + 9) = (7 + 8 + 9) \times (3 - 1) = (7 + 8 + 9) \times 2 = 24 \times 2 = 48

Thus, the final result is \boxed{48}.

Related Problems
Problem 2 AMC 8 Daily Practice - Calculation Tricks by Grouping
Problem 3 AMC 8 Daily Practice - Calculation Tricks by Grouping
Problem 4 AMC 8 Daily Practice - Calculation Tricks by Grouping
Problem 5 AMC 8 Daily Practice - Calculation Tricks by Grouping
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