Question 1102348
Let {{{ n = 0 }}} when he was {{{ 6 }}} yrs old
{{{ n = 4 }}} when he was {{{ 10 }}} yrs old
Let {{{ S }}} = number of books he read 
from age {{{ 6 }}} to age {{{ 10 }}}
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{{{ S = 6*( 2^( n+1 ) - 1 ) }}} and {{{ n = 4 }}}
{{{ S = 6*( 2^5 - 1 ) }}}
{{{ S = 6*( 32 - 1 ) }}}
{{{ S = 6*31 }}}
{{{ s = 186 }}}
He read 186 books from age {{{ 6 }}} to age {{{ 10 }}}
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check:
{{{ S = 6*2^0 + 6*2^1 + 6*2^2 + 6*2^3 + 6*2^4 }}}
{{{ S = 6 + 6*2 + 6*4 + 6*8 + 6*16}}}
{{{ S = 6 + 12 + 24 + 48 + 96 }}}
{{{ S = 186 }}}
OK