Question

length of a rectangular blackboard is 8m more than its breadth. if it's length is increased by 7m and breadth of decreased by 4m, it's area remains unchanged. what is the length of the blackboard

Answer 1

7x
${7x}^{2} - 20x + 32$

Answer 2

Here area of first rectangle is equal to the area of secound.
therefore
$(x - 4)(x + 15) = (x)(x - 4)$
therefore
x^2 - 4x +15x -60 = x^2 + 8x.
cancel x^2
=-4x + 15x -60 = 8x
=11x -8x = 60
= 3x = 60
therfore
x= 20.
but this is breadth and we have to find out the length which is x + 8
therefore ans is 28.
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