Question 648179
Just think of one plane as standing still and
the other moving away at the sum of their speeds.
{{{ 2100 = ( 560 + 640 )*t }}}
{{{ t = 2100 / 1200 }}}
{{{ t = 1.75 }}} hrs
{{{ .75 }}} hr = 45 min
10:30 + 1:45 = 12:15
They will be 2100 km at 12:15 PM
check answer:
plane #1
{{{ d[1] = 560*1.75 }}}
{{{ d[1] = 980 }}}
plane #2
{{{ d[2] = 640*1.75 }}}
{{{ d[2] = 1120 }}}
{{{ d[1] + d[2] = 980 + 1120 }}}
{{{ 980 + 1120 = 2100 }}}
OK