Question 722167
Let {{{ r }}} = the number of rows
{{{ r + 4 }}} = the number of chairs /row
{{{ r*( r + 4 ) = 96 }}}
{{{ r^2 + 4r = 96 }}}
Complete the square
{{{ r^2 + 4r + (4/2)^2 = 96 + (4/2)^2 }}}
{{{ r^2 + 4r + 4 = 96 + 4 }}}
{{{ r^2 + 4r + 4 = 100 }}}
{{{ ( r + 2 )^2 = 10^2 }}}
take the square root of both sides
{{{ r + 2 = 10 }}}
{{{ r = 8 }}}
{{{ r + 4 = 12 }}}
The number of rows is 8
The number of chairs /row is 12
Check:
{{{ 8 * 12 = 96 }}}
OK