Scaling up from a Numerator and Denominator to a Triple RatioDate: 07/08/2011 at 07:56:38 From: Jon Subject: Ratio and Proportion The ratio of mango trees to guava trees to apple trees in an orchard is 4:3:5. If there are 960 trees in the orchard, how many of each kind of tree are there? a. 320; 240; 400 b. 120; 240; 360 c. 240; 360; 480 d. 120; 280; 340 e. 20; 40; 60 Fractions typically consist of only two parts, but this problem presents three unknowns in proportion with one another. I've tried number of mango trees = 960/4 = 240 number of guava trees = 960/3 = 320 number of apple trees = 960/5 = 192 But this answer is not one of the choices given. Please help on how to solve this. Date: 07/08/2011 at 08:20:33 From: Doctor Jerry Subject: Re: Ratio and Proportion Hello Jon, Thanks for writing to Dr. Math. We know that m:g:a = 4:3:5 According to what "triple ratios" mean, this is equivalent to some constant, k, equaling m/4 = g/3 = a/5 So, m = 4k g = 3k a = 5k Then, 4k + 3k + 5k = 960 12k = 960 k = 80 Now, m = 4*k = 320 and so on. Please feel free to write back -- using the URLs at the bottom of this message -- if you have questions relative to my comments. - Doctor Jerry, The Math Forum http://mathforum.org/dr.math/ |
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