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Math Help - Please Help! I'm not sure what category this comes under!

  1. #1
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    Exclamation Please Help! I'm not sure what category this comes under!

    Looking at the other threads, I'm pretty sure this'll seem easy to you guys. But i'm really stuck. i mean, i don't even know how to go about working this thing out.

    "Katie has a new job as a primary school teacher. as part of a science experiment, she helped all 30 of her students to plant a seed each. after one week, the class measured their plants' heights to the nearest centimetre Several of the classes' plants had grown to 5cm. A smaller number had grown to 2cm. The rest, including micky's plant, had only grown 1cm. The class added up the total height of all plants.
    after another week they measured again. all the plants except Micky's had doubled in size, where his was still only 1cm. The class added up the total heights of their plants which came to 131cm.
    How many plants of each height were there after the first week?"

    Thanks for any help in advance. :]
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  2. #2
    MHF Contributor
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    Quote Originally Posted by Laura.Kim View Post
    "Katie has a new job as a primary school teacher. as part of a science experiment, she helped all 30 of her students to plant a seed each. after one week, the class measured their plants' heights to the nearest centimetre Several of the classes' plants had grown to 5cm. A smaller number had grown to 2cm. The rest, including micky's plant, had only grown 1cm. The class added up the total height of all plants. after another week they measured again. all the plants except Micky's had doubled in size, where his was still only 1cm. The class added up the total heights of their plants which came to 131cm.

    How many plants of each height were there after the first week?"
    At the end, Micky's plant was 1 cm tall. Subtract this from the total. What then was the total of the other twenty-nine plants?

    At the end of the first week, the other plants had been 1, 2, or 5 centimeters tall. These other plants all doubled in height. What were the new heights?

    At this point, I believe you're left with guess-n-check for finding a combination that will work, since there isn't enough information to form a system of equations that can be solved for a unique value. One way to start would be with values "in the middle", such as 10 of the shortest height, 9 of the middling height, and 10 of the tallest height. Then adjust until you can find a combination that works.

    Have fun!
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