Question 944759
Let {{{ s }}} = the woman's speed in km/hr
Let {{{ d }} = the distance the boy travels in 15 minutes 
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Convert minutes to hours
{{{ 15/60 = 1/4 }}} hrs
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{{{ d = 4*(1/4) }}}
{{{ d = 1 }}} km
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Convert meters to km
{{{ 125/1000 = 1/8 }}} km
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The woman's equation is:
{{{ 1 - 1/8 = s*( 1/4 ) }}}
{{{ 7/8 = s*( 1/4 ) }}}
Multiply both sides by {{{ 4 }}}
{{{ s = 7/2 }}}
{{{ s = 3.5 }}}
The woman's speed is 3.5 km/hr
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check:
At her rate, in 1/4 hr, she travels {{{ ( 7/2 )/4 = 7/8 }}} km
{{{ 1 - 7/8 = 1/8 }}} km which was her head start
OK