document.write( "Question 174113: the four oldest people in Golden City lived a total of 384 years put together. The difference in ages for the youngest and the second oldest is 14. The second youngest is 3 years older than the youngest. The oldest is 20 years older than the average of the second and youngest. What are their ages? \n" ); document.write( "
Algebra.Com's Answer #129020 by gonzo(654)![]() ![]() ![]() You can put this solution on YOUR website! youngest = a \n" ); document.write( "second youngest = b \n" ); document.write( "second oldest = c \n" ); document.write( "oldest = d \n" ); document.write( "----- \n" ); document.write( "all four lived a total of 384 years.: \n" ); document.write( "a + b + c + d = 384 \n" ); document.write( "----- \n" ); document.write( "difference in ages for the youngest and the second oldest is 14: \n" ); document.write( "c - a = 14 \n" ); document.write( "----- \n" ); document.write( "the second youngest is 3 years older than the youngest. \n" ); document.write( "b = a + 3 \n" ); document.write( "----- \n" ); document.write( "The oldest is 20 years older than the average of the second and youngest. \n" ); document.write( "***** \n" ); document.write( "question here is second what? \n" ); document.write( "second youngest or second oldest. \n" ); document.write( "i'll have to solve for both to see. \n" ); document.write( "if second oldest, then: \n" ); document.write( "d = (c+a)/2 + 20 \n" ); document.write( "if second youngest, then: \n" ); document.write( "d = (b+a)/2 + 20 \n" ); document.write( "----- \n" ); document.write( "equations you have to work with are: \n" ); document.write( "a + b + c + d = 384 \n" ); document.write( "c = a + 14 (derived from c-a = 14) \n" ); document.write( "b = a + 3 \n" ); document.write( "---- \n" ); document.write( "before we go any further, we will substitute: \n" ); document.write( "a + 14 for c, and: \n" ); document.write( "a + 3 for b \n" ); document.write( "----- \n" ); document.write( "a + b + c + d becomes: \n" ); document.write( "a + a + 3 + a + 14 + d = 384 \n" ); document.write( "if we combine like terms, this equation becomes: \n" ); document.write( "3*a + 17 + d = 384 \n" ); document.write( "----- \n" ); document.write( "we have also: \n" ); document.write( "d = (c+a)/2 + 20 \n" ); document.write( "or: \n" ); document.write( "d = (b+a)/2 + 20 \n" ); document.write( "----- \n" ); document.write( "we'll look at d = (b+a)/2 + 20 first. \n" ); document.write( "we start with: \n" ); document.write( "d = (b+a)/2 + 20 \n" ); document.write( "we substitute a+3 for b: \n" ); document.write( "d = (a + 3 + a)/2 + 20 \n" ); document.write( "we combine like terms: \n" ); document.write( "d = (2*a + 3)/2 + 20 \n" ); document.write( "we substitute for d in the total equation: \n" ); document.write( "3*a + 17 + d = 384 \n" ); document.write( "becomes: \n" ); document.write( "3*a + 17 + (2*a+3)/2 + 20 = 384 \n" ); document.write( "we combine like terms: \n" ); document.write( "3*a + 37 + (2*a+3)/2 = 384 \n" ); document.write( "we multiply by 2 to remove fractions: \n" ); document.write( "6*a + 74 + 2*a + 3 = 768 \n" ); document.write( "we combine like terms: \n" ); document.write( "8*a + 77 = 768 \n" ); document.write( "we subtract 77 from both sides: \n" ); document.write( "8*a = 768 - 77 \n" ); document.write( "we combine like terms: \n" ); document.write( "8*a = 691 \n" ); document.write( "a = 86.375 \n" ); document.write( "----- \n" ); document.write( "i was looking for an integer. \n" ); document.write( "before going further, i'll try the second option. \n" ); document.write( "that was: \n" ); document.write( "d = (c+a)/2 + 20 \n" ); document.write( "----- \n" ); document.write( "we start with: \n" ); document.write( "d = (c+a)/2 + 20 \n" ); document.write( "we substitute for c: \n" ); document.write( "d = (a + 14 + a)/2 + 20 \n" ); document.write( "we substitute for d in the total equation: \n" ); document.write( "3*a + 17 + d = 384 \n" ); document.write( "becomes: \n" ); document.write( "3*a + 17 + (2*a + 14)/2 + 20 = 384 \n" ); document.write( "we remove parentheses: \n" ); document.write( "3*a + 17 + 2*a/2 + 14/2 + 20 = 384 \n" ); document.write( "we simplify: \n" ); document.write( "3*a + 17 + a + 7 + 20 = 384 \n" ); document.write( "we combine like terms: \n" ); document.write( "4*a + 44 = 384 \n" ); document.write( "we subtract 44 from both sides: \n" ); document.write( "4*a = 384 - 44 \n" ); document.write( "we simplify: \n" ); document.write( "4*a = 340 \n" ); document.write( "we divide both sides by 4 \n" ); document.write( "a = 340/4 = 85 \n" ); document.write( "----- \n" ); document.write( "this option looks more promising so we'll pursue further. \n" ); document.write( "we used the equation for: \n" ); document.write( "The oldest is 20 years older than the average of the second OLDEST and youngest. \n" ); document.write( "to solve for d: \n" ); document.write( "d = (c+a)/2 + 20 \n" ); document.write( "----- \n" ); document.write( "we have a = 85 \n" ); document.write( "c = a + 14 = 85 + 14 = 99 \n" ); document.write( "c = 99 \n" ); document.write( "----- \n" ); document.write( "b = a + 3 = 85 + 3 = 88 \n" ); document.write( "b = 88 \n" ); document.write( "----- \n" ); document.write( "d = (c+a)/2 + 20 = (99 + 85)/2 + 20 = 184/2 + 20 = 92 + 20 = 112 \n" ); document.write( "d = 112 \n" ); document.write( "----- \n" ); document.write( "a = 85 \n" ); document.write( "----- \n" ); document.write( "a + b + c + d = 85 + 88 + 99 + 112 = 384 \n" ); document.write( "----- \n" ); document.write( "the equation appears to be satisfied. \n" ); document.write( "youngest is 85 \n" ); document.write( "second youngest is 88 \n" ); document.write( "second oldest is 99 \n" ); document.write( "oldest is 112 \n" ); document.write( "----- \n" ); document.write( "i also solved for: \n" ); document.write( "d = (a+b)/2 + 20 \n" ); document.write( "which was: \n" ); document.write( "The oldest is 20 years older than the average of the second YOUNGEST and youngest. \n" ); document.write( "the answer came out different but i was still able to solve it and got an answer that also makes sense except that the ages are not in whole integers. \n" ); document.write( "here's how that worked: \n" ); document.write( "d = (a+b)/2 + 20 \n" ); document.write( "we substitute for b: \n" ); document.write( "d = (a + a + 3)/2 + 20 \n" ); document.write( "we substitute for d in the total equation: \n" ); document.write( "3*a + 17 + d = 384 \n" ); document.write( "becomes: \n" ); document.write( "3*a + 17 + (2*a + 3)/2 + 20 = 384 \n" ); document.write( "we combine like terms: \n" ); document.write( "3*a + 37 + (2*a + 3)/2 = 384 \n" ); document.write( "we subtract 37 from both sides: \n" ); document.write( "3*a + (2*a + 3)/2 = 347 \n" ); document.write( "we multiply both sides by 2 to get: \n" ); document.write( "6*a + 2*a + 3 = 2*347 \n" ); document.write( "we combine like terms and simplify: \n" ); document.write( "8*a + 3 = 694 \n" ); document.write( "we subtract 3 from both sides: \n" ); document.write( "8*a = 691 \n" ); document.write( "we divide both sides by 8: \n" ); document.write( "a = 691/8 = 86.375 \n" ); document.write( "b = a + 3 = 89.375 \n" ); document.write( "c = a + 14 = 100.375 \n" ); document.write( "d = (a+b)/2 + 20 = (86.375 + 89.375)/2 + 20 = 175.75/2 + 20 =87.875 + 20 = 107.875 \n" ); document.write( "----- \n" ); document.write( "we have: \n" ); document.write( "a = 86.375 \n" ); document.write( "b = 89.375 \n" ); document.write( "c = 100.375 \n" ); document.write( "d = 107.875 \n" ); document.write( "add them all up together and we get: \n" ); document.write( "384 \n" ); document.write( "----- \n" ); document.write( "whether we used second oldest or second youngest in solving for d, we had a solution either way. \n" ); document.write( "----- \n" ); document.write( "choose the one that applies to your problem. \n" ); document.write( "-----\r \n" ); document.write( "\n" ); document.write( " \n" ); document.write( " |