sheung asked in 科學及數學數學 · 1 decade ago

maths question(f.4)

the lower base of a trapezium is longer than its upper base by 4 cm and its height is 2 times its upper base.If the area of the trapezium is 70 cm^2, find its upper base.

Update:

to 001: [x+(x+4)*(2x)]/2=70 isn't correct

is [(x+(x+4))*(2x)]/2=70

1 Answer

Rating
  • 1 decade ago
    Favorite Answer

    Let the upper base be x

    [x+(x+4)*(2x)]/2=70

    x=5 or x=-7 (rejected)

    2010-08-23 15:59:29 補充:

    Base on the formula of trapezium,[(upper base+lower base)x height]/2 = Area

    2010-08-23 16:03:55 補充:

    -7 is not an appropriate answer because it is smaller than zero.But for the ''area/perimeter'' cases, answer must be a positive number.

    2010-08-23 16:50:32 補充:

    To 002: Although you can list the right equation on this question,your step are wrong.

    Step3 and 4, 2x^2+4x=70 is not equal to 2x^2-4x-70=0

    2010-08-23 16:51:23 補充:

    your steps are wrong****

    2010-08-23 17:08:42 補充:

    Sorry,I don't know why my supplementary content was deleted.

    Note that base on the formula of trapezium ,Area=[(lower base+upper base)xheight]/2

    And for any ''area or perimeter'' Question, We would like take the positive number while negative number must be rejected.

    2010-08-23 17:08:54 補充:

    To 002: Although you can list the right equation on this question,your steps are wrong.

    In step3 and step 4, 2x^2 + 4x = 70 is not equal to 2x^2 - 4x - 70 = 0.It should be 2x^2+4x-70=0.

Still have questions? Get your answers by asking now.