Question 1028975
Add their rates of filling
to get rate filling together
rate fore each machine = 
[ daily quota ] / [ time to fill the quota ]
Let {{{ t }}} = time in hrs to fill quota
with all 3 machines working
{{{ 1/90 + 1/99 + 1/110 = 1/t }}}
Multiply both sides by {{{ 90*99 *110*t }}}
{{{ 99*110*t + 90*110*t + 90*99*t = 90*99*110 }}}
{{{ 10890t + 9900t + 8910t = 980100 }}}
{{{ 29700t = 980100 }}}
{{{ t = 33 }}}
with all three machines working, you can 
fill the daily quota of water bottles in 33 hrs
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check answer:
{{{ 1/90 + 1/99 + 1/110 = 1/t }}}
{{{ 1/90 + 1/99 + 1/110 = 1/33 }}}
{{{ .011111 + .010101 + .009090 = .030303 }}}
{{{ .030302 = .030303 }}}
OK -error due to rounding off