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Posted by on Tuesday, February 16, 2010 at 11:36am.

The length of a rectangle is fixed at 18 cm. What widths will make the perimeter greater than 78 cm.?
*widths must be greater than __cm.
I have been working at this for two hours and even after reviewing my readings I am just as confused as ever.

  • College Algebra - , Tuesday, February 16, 2010 at 11:41am

    Perimeter equals two times length plus two times width.

    P = 2L + 2W

    78 = 2(18) + 2W
    78 = 36 + 2W
    42 = 2W
    21 = W

  • College Algebra - , Tuesday, February 16, 2010 at 11:46am

    ..so I want to multiply 18 by two to get 36?
    I got that..I am stuck on the area that says "what widths will make the perimeter greater than 78 cm?"..I appreciate your response, but am still confused..math is my downfall for sure.
    Is my final answer of 42 correct or do I divide it my 2 (which is how I understood you did it) why divide by 2?

  • College Algebra - , Tuesday, February 16, 2010 at 11:55am

    How could your final answer be 42 for the width? The width must be shorter than the length.

    Draw a rectangle. Label the two long sides as 18 cm. You need to find the length of each of the two short sides.

  • College Algebra - , Tuesday, February 16, 2010 at 12:05pm

    okay..I drew the rectangle..18*2=36 length.
    The widths must make the perimeter greater than 78 cm..
    I took 78-36 to get 42 and divided it by 2 for the two width sides and got 21. You stated that the width must be shorter than the length..21 cm is not shorter than 18 (Length)..so I am still confused..I'm sorry..thanks for your help..any insight as to what I am doing wrong?

  • College Algebra - , Tuesday, February 16, 2010 at 12:11pm

    I got confused too. The problem is misstated.

    The WIDTH must be 18.

    The LENGTH must be 21.

  • College Algebra - , Tuesday, February 16, 2010 at 12:33pm

    Thank you again Ms. Sue for your help..math makes me crazy :)

  • College Algebra - , Tuesday, February 16, 2010 at 12:38pm

    You're welcome. But you're on the right track. Hang in there, Tanya.

  • College Algebra - , Sunday, March 28, 2010 at 9:34pm

    What is the formula for the volume of a rectangular solid? Find an object in your residence that has the shape of a rectangular solid. Measure and record the length, width, and height of your object in either centimeters (to the nearest 10th of a centimeter) or inches (to the nearest quarter of an inch). Compute the volume of your solid and include units with your answer

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