SOLUTION: A rectangle is such that the lengths of its adjacent sides differ by 5cm. A similar rectangle measures 18cm by 28cm. Find the length and breadth of the first rectangle.

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Question 696725: A rectangle is such that the lengths of its adjacent sides differ by 5cm. A similar rectangle measures 18cm by 28cm. Find the length and breadth of the first rectangle.
Answer by KMST(5328) About Me  (Show Source):
You can put this solution on YOUR website!
x = width of the first rectangle
x%2B5 = length of the first rectangle
%28x%2B5%29%2Fx=28%2F18 --> 18%28x%2B5%29=28x --> 18x%2B90=28x --> 18x%2B90-18x=28x-18x --> 90=10x --> 90%2F10=10x%2F10 --> highlight%28x=9%29
x%2B5=9%2B5 --> x%2B5=14 --> length of the first rectangle = highlight%2814%29

Actually, for mental math, the ratio of corresponding sides is the same and also equal to the ratio of the differences in length, so I mentally calculated
x%2F18=5%2F%2828-18%29=5%2F10=1%2F2 and immediately knew that the dimensions of the first rectangle were half of the dimensions of the other one.