document.write( "Question 1070012: john age is a multiple of 7 this year. in 3 years time, his age will be a muiltiple of 5. his age is between 20 and 70, how old will john be in 6 years time? \n" ); document.write( "

Algebra.Com's Answer #685109 by KMST(5328) $\"\"$ $\"About$

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ONE WAY:
\n" ); document.write( "The multiples of 7 between 20 and 70 are
\n" ); document.write( "21, 28, 35, 42, 49, 56, 63,
\n" ); document.write( "(and if it was between 20 and 70 inclusive,
\n" ); document.write( "also 70.
\n" ); document.write( "35 and 7p are multiples of 5,
\n" ); document.write( "and would not be if wee add 3.
\n" ); document.write( "The other numbers, with 3 added are
\n" ); document.write( "24, 31, 45, 52, 59, and 66.
\n" ); document.write( "The only one of those that is s multiple of 5
\n" ); document.write( "is $\"42\"$ , and in $\"6\"$ years
\n" ); document.write( "he will be $\"42=6%2Bhighlight%2848%29\"$ ,
\n" ); document.write( "so John is 42.
\n" ); document.write( "
\n" ); document.write( "A FANCY WAY:
\n" ); document.write( " $\"7n\"$ = John's age now,
\n" ); document.write( "with $\"n\"$ being a whole number.
\n" ); document.write( "We are told that $\"20%3C=7n%3C=70\"$ ,
\n" ); document.write( "so $\"20%2F7%3C=n%3C=70%2F7\"$ --> $\"3%3C=n%3C=10\"$ .
\n" ); document.write( " $\"7n%2B3\"$ = John's age in $\"3%7D%7D+years.%0D%0A%7B%7B%7B7n%2B3=5n%2B2n%2B3=5n%2B2%28n-1%29%2B2%2B3=5n%2B5%2B2%28n-1%29\"$
\n" ); document.write( "The only way that sum can be a multiple of $\"5\"$
\n" ); document.write( "is of $\"2%28n-1%29\"$ , and therefore $\"n-1\"$
\n" ); document.write( "are multiples off $\"5\"$ ,
\n" ); document.write( "and with $\"3%3C=n%3C=10\"$ <--> $\"2%3C=n-1%3C=9\"$ ,
\n" ); document.write( "the only choice is $\"n-1=5\"$ .
\n" ); document.write( "So, $\"n=5%2B1=6\"$ and $\"7n=7%2A6=42\"$ .
\n" ); document.write( "In 6 years time, John will be
\n" ); document.write( " $\"42%2B6=highlight%2848%29\"$ . \n" ); document.write( "

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