Question 1110174
{{{ s }}} = the speed of the slower plane
{{{ s + 18 }}} = the speed of the faster plane
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You can think of this as one of the planes
flying at the sum of their speeds, and the
other plane standing still
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{{{ 1179 = ( s + s + 18 )*1.5 }}}
{{{ 1179 = ( 2s + 18 )*1.5 }}}
{{{ 1179 = 3s + 27 }}}
{{{ 3s = 1152 }}}
{{{ s = 384 }}}
and
{{{ s + 18 = 384 + 18 }}}
{{{ s + 18 = 402 }}}
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The rates of the planes are 384 mi/hr and 402 mi/hr
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check the answer:
{{{ d[1] = 384*1.5 }}}
{{{ d[1] = 576 }}}
and
{{{ d[2] = 402*1.5 }}}
{{{ d[2] = 603 }}}
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{{{ d[1] + d[2] = 576 + 603 }}}
{{{ d[1] + d[2] = 1179 }}}
OK