document.write( "Question 287596: Hannah, Mark and Tom have a combined age of 68. Hannah is twice as old as the difference between Mark and Tom's age. Mark and Tom's combined age is 16 times
\n" ); document.write( "Hannah's age. Mark is older than Tom. How old is Tom?\r
\n" ); document.write( "\n" ); document.write( "(a) 31 (b) 32 (c) 33 (d) 34 (e) None of the above\r
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Algebra.Com's Answer #208446 by Deina(147)\"\" \"About 
You can put this solution on YOUR website!
First, let's put this in a form where we can see what we're looking for:

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  • Hannah, Mark and Tom have a combined age of 68. So:
    \n" ); document.write( "H + M + T = 68

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  • Hannah is twice as old as the difference between Mark and Tom's age.
    \n" ); document.write( "H = 2(|M - T|)

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  • Mark and Tom's combined age is 16 times Hannah's age.
    \n" ); document.write( "M + T = 16(H)

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  • Mark is older than Tom.

\n" ); document.write( "Now we have a series of equations that we can solve:
\n" ); document.write( "H + M + T = 68
\n" ); document.write( "H = 2(M - T)
\n" ); document.write( "M + T = 16(H)

\n" ); document.write( "The 1st thing that I see is the similarity between the 1st & 3rd equations:
\n" ); document.write( "\"+H+%2B+M+%2B+T+=+68+\"
\n" ); document.write( "\"+M+%2B+T+=+16%28H%29\" so
\n" ); document.write( "\"+%28H+%2B+M+%2B+T%29-+H+=+68+-+H+\" Subtract H from both sides, giving us:
\n" ); document.write( "\"+M+%2B+T+=+68+-+H+\"
and from the 3rd equation we know that:
\n" ); document.write( "\"+M+%2B+T+=+16%28H%29\" so
\n" ); document.write( "\"+16%28H%29+=+68+-+H+\" Add H to each side and:
\n" ); document.write( "\"+17%28H%29+=+68+\"
Divide both sides by 17 and we find that:
\n" ); document.write( "H = 4 So Hannah is 4 years old.

\n" ); document.write( "\"+M+%2B+T+=+68+-+H+\" So \"+M+%2B+T+=+64+\"
\n" ); document.write( "From the 4th clue we know that Mark is older than Tom, and from the 2nd equation we know that:
\n" ); document.write( "\"+4%2F2+=+%282%28M+-+T%29%29%2F2+\" so \"+2+=+M+-+T+\"we now know that the difference between Mark & Tom's age is 2 years

\n" ); document.write( "So taking our \"+M+%2B+T+=+64+\", we will substitute Tom's age + 2 for Marks age (and reverse their order, just to clarify things):
\n" ); document.write( "\"+T+%2B+T+%2B+2+=+64+\" = \"+2T+%2B+2+=+64+\" Subtract 2 from each side, then divide each side:

\n" ); document.write( "\"+2T%2F2+=+62%2F2+\" so Tom is 31 years old, making Mark = 33

\n" ); document.write( "Substitute those numbers back into the equations to check, reread the problem to make sure you're answering the right question and bob's your uncle!\r
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