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QUESTION: I WOULD LIKE TO KNOW HOW TO GO ABOUT COMPUTING THE PERCENTAGES, IF FOR EXAMPLE JOHN MADE A $250 IN CONTRIBUTION TO A BUILDING PROJECT THAT COST $3000, MEANING HIS PERCENTAGE CONTRIBUTION IS 8.333%, IF HE ALSO MAKES A $300 CONTRIBUTION TO PURCHASE FURNITURE WHICH COST $2250 TO BEAUTIFY THE BUILDING, MEANING HIS PERCENTAGE CONTRIBUTION IS 13.333%. HOW DO YOU FIND HIS TOTAL PERCENTAGE OF THE TWO PROJECTS(BUILDING AND FURNITURE)WHICH COST $5250 IN TOTAL.

ANSWER: John contributed $250 towards the $3000 costs to start. This happens to be 250/300 or 8.33%. He then contributed $300 towards the subsequent $2250 cost, or 300/2250 = 13.33%. The total contribution by John is $550 towards a total cost of $5250, so just like you calculated the percentages for the 2 pieces of the projects, John's total contribution to the total project is $550/$5250 = 10.48%.

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QUESTION: Can you then say that just like you added his contribution to get $550 then you can add the two percentages (8.33% and 13.33)and because it is for 200% (two different contributions) then finding the 100% of the sum of the two percentile would be 10.83 which when computer against the total amount ($5250)you get $568.575 which is 18.575 more that the actual. this is my challenge, is it possible to go the way i went?

The 2 cases have different amounts of money contributing to the total: $3000 + $2250 = $5250. You have to weight the percentages according the the fraction of the total that they correspond to:

(3000/5250)(8.33%) + (2250/5250)(13.33%) = 10.48%.

Your method is weights the 2 contributions equally which is why you get a different (erroneous) answer.

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“A Numerical Model for Low-Frequency Equatorial Dynamics” (with Mark A. Cane), J. of Phys. Oceanogr., 14, No. 12, pp. 18531863, December 1984.**Education/Credentials**

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