Question 1154015
Let {{{ s }}} = speed in still water
Let {{{ c }}} = speed of the current
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(1) {{{ 28 = ( s + c )*2 }}}
(2) {{{ 24 = ( s - c )*4 }}}
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(1) {{{ 2s + 2c = 28 }}}
(2) {{{ 4s - 4c = 24 }}}
Multiply both sides of (1) by {{{2}}}
and add the equations
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(1) {{{ 4s + 4c = 56 }}}
(2) {{{ 4s - 4c = 24 }}}
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{{{ 8s = 80 }}}
{{{ s = 10 }}}
and
(1) {{{ 2s + 2c = 28 }}}
(1) {{{ 2*10 + 2c = 28 }}}
(1) {{{ 2c = 8 }}}
(1) {{{ c = 4 }}}
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speed in still water?
The boat travels at 10 miles per hour in still water. 
What is the speed of the current of the river? 
The speed of the current is 4 miles per hour.