Question 1133824
Add their rates of working to get
their rate working together
1st rate:
[ 1 problem solved ] / [ 75 min ]
2nd rate:
[ 1 problem solved ] / [ 50 min ]
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Let {{{ 1/t }}} = their rate working together
in problems/min
{{{ 1/75 + 1/50 = 1/t }}}
Multiply both sides by {{{ 150t }}}
{{{ 2t + 3t = 150 }}}
{{{ 5t = 150 }}}
{{{ t = 30 }}}
It takes them 30 min working together
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check:
{{{ 1/75 + 1/50 = 1/30 }}}
{{{ 1/15 + 1/10 = 1/6 }}}
{{{ .06667 + .1 = .16667 }}}
{{{ .16667 = .16667 }}}
OK