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An elementary school has a large lunch room containing many tables. One day at lunch, the children at one table decide to see how long it will take to spread a rumor throughout the entire room. Each minute, the number of tables that know the rumor doubles in size. If it takes just 10 minutes for the rumor to reach every table in the room, how long will it take for the rumor to reach half of the tables in the room?

  • math -

    1 min.: 1 Table = 2^0 = 2^(t-1).
    2 " : 2 " = 2^1 = 2^(t-1).
    3 " : 4 " = 2^2 = 2^(t-1).
    10" : n " = 2^(10-1)

    10-1 = 9 min. to do all of the tabls.
    9-1 = 8 Min. to do 1/2 of the tables.

    CHECK:
    2^9 = 512 Tables.
    2^8 = 256 Tables.

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