Question 975161
Let {{{ s }}} = actual speed in km/hr
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Convert time to hrs
{{{ 40/60 = .6667 }}} hrs
{{{ 48/3600 = .01333 }}} hrs
{{{ 1 + .6667 + .01333 = 1.68 }}} hrs
{{{ 42 = (( 5/7 )*s )* 1.68 }}}
{{{ 7*42 = 5s*1.68 }}}
{{{ 294 = 8.4s }}}
{{{ s = 35 }}}
The actual speed is 35 km/hr
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check:
{{{ ( 5/7 )*35 = 25 }}} km/hr
{{{ 42 = (( 5/7 )*s )* 1.68 }}}
{{{ 42 = 25* 1.68 }}}
{{{ 1.68 = 1.68 }}}
OK