SOLUTION: If the three sides of a triangle are in a ratio 3:5:7 and the perimeter of the triangle is 12cm, what is the length of the longest side?

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Question 929622: If the three sides of a triangle are in a ratio 3:5:7 and the perimeter of the triangle is 12cm, what is the length of the longest side?
Found 2 solutions by jim_thompson5910, LinnW:
Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!
hint:

solve for x

3x+5x+7x = 12

then compute 7x to get your answer

Answer by LinnW(1048) About Me  (Show Source):
You can put this solution on YOUR website!
With side ratio 3:5:7 , first add the numbers together.
This will give us a denominator to find fractional parts.
3+5+7 = 15
The shortest side will be 3/15 * 12 = 36/15 = 2.4
Then next side will be 5/15 * 12 = 60/15 = 4
The last side will be 7/15 * 12 = 84/15 = 5.6
Notice that 2.4:4:5.6 is equivalent to 3:5:7
2.4:4:5.6 , multiplying each element by 10
gives us 24:40:56
Divide each by 8 and we get
3:5:7