<PRE><B>Question 585848</B>
If A mowed 3/4 of his lawn, there is 1/4 left 
for B to mow
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If A mowed a lawn 4 times as large, it would take him
4 times longer, so
{{{ 4*(3/4) = 3 }}} lawns take him {{{ 4*(5/4) = 5 }}} hrs
1 lawn would take him 1/3 of that time, or {{{ (1/3)*5 = 5/3 }}} hrs
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If B works twice as fast, he can mow 1 lawn in {{{ (1/2)*(5/3) = 5/6 }}} hrs
But B only has to mow 1/4 of a lawn, so
B can mow it in {{{ (1/4)*(5/6) = 5/24 }}} hrs
{{{ 5/24 }}} hrs x {{{ 60 }}} min/hr = 12.5 minutes</PRE>