Question 1065360
Old sweeper's rate:
[ 1 job ] / [ 60 hrs ]
New sweeper's rate:
[ 1 job ] / [ t hrs ]
Their rate working together:
[ 1 job ] / [ 15 hrs ]
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Add their rates of working to get
their rate working together
{{{ 1/60 + 1/t = 1/15 }}}
Multiply both sides by {{{ 60t }}}
{{{ t + 60 = 4t }}}
{{{ 3t = 60 }}}
{{{ t = 20 }}}
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The new sweeper does the job in 20 hrs
working alone
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check:
{{{ 1/60 + 1/20 = 1/15 }}}
Multiply both sides by {{{ 60 }}}
{{{ 1 + 3 = 4 }}}
{{{ 4 = 4 }}}
OK