Question 635240
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Hi,
The perimeter of a triangle is 90 cm
The lengths of the sides of the triangle are in the ratios 3 : 5 : 7 
 3k + 5k + 7k = 90cm     | Letting k be the constant of the proportion
         15k = 90cm
           k = 6cm
 {{{7*6cm = 42cm}}}, the longest side
and...
 {{{18 + 30 + 42 = 90}}}