Question 561275
{{{ 7/15 + 5/12 }}}
The only factor that is common to both {{{ 12 }}} and {{{15 }}}
is {{{ 3 }}}, since {{{ 3*4 = 12 }}} and {{{ 3*5 = 15 }}}
I'll try {{{ 12*15 }}} for an LCD, but I'll divide it by the
common factor of {{{ 3 }}}.
{{{ ( 12*15 )/3 = 4*15 }}}
{{{ 4*15 = 60 }}}
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Multiply the top and bottom of {{{ 7/15 }}} by {{{ 4 }}}
{{{ (4/4)*(7/15) = 28/60 }}}
Multiply the top and bottom of {{{ 5/12 }}} by {{{ 5 }}}
{{{ (5/5)*(5/12) = 25/60 }}}
{{{ 28/60 + 25/60 = 53/60 }}} answer
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An easy way to check this is to use decimals from calculator:
{{{ 7/15 = .4666667 }}}
{{{ 5/12 = .4166667 }}}
{{{ 7/15 + 5/12 = .8833333 }}}
and
{{{ 53/60 = .8833333 }}}
OK