Question 749934
Let {{{ k }}} = Kat's age now in years
The difference in our ages is ( and always was )
{{{ 40 - k }}}
When I was as old as Kat is now, I was {{{ k }}} years old
Kat is younger by the difference in our ages, so Kat was
{{{ k - ( 40 - k ) = 2k - 40 }}}
I am twice as old as that now, so I am
{{{ 2*( 2k - 40 ) }}}
I am {{{ 40 }}} now, so
{{{ 2*( 2k - 40 ) = 40 }}}
{{{ 4k - 80 = 40 }}}
{{{ 4k = 120 }}}
{{{ k = 30 }}}
Kat is 30
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check answer:
When I was as old as Kat is now, I was {{{ 30 }}}
That was {{{ 10 }}} years ago, so Kat was {{{ 20 }}}
Am I twice that age? Yes, I am {{{ 40 }}}
OK