Question 947422
Let {{{ s }}} = the speed of the fish in meters/min
Let {{{ c }}} = the speed oif the current in meters/min
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Equation for downstream:
(1) {{{ 100 = ( s + c )*8 }}}
Equation for upstream:
(2) {{{ 100 = ( s  - c )*20 }}}
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(1) {{{ s + c = 25/2 }}}
and
(2) {{{ s - c = 5 }}}
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Add the equations
{{{ 2s = 10/2 + 25/2 }}}
{{{ 2s = 35/2 }}}
{{{ s = 35/4 }}}
{{{ s = 8.75 }}}
and
(1) {{{ 35/4 + c = 25/2 }}}
(1) {{{ c = 50/4 - 35/4 }}}
(1) {{{ c = 15/4 }}}
(1) {{{ c = 3.75 }}}
The speed of the fish is 8.75 meters/min
The speed oif the current is 3.75 meters/min
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check:
(2) {{{ s - c = 5 }}}
(2) {{{ 8.75 - 3.75 = 5 }}}
(2) {{{ 5 = 5 }}}
and
(1) {{{ 100 = ( s + c )*8 }}}
(1) {{{ 100 = ( 8.75 + 3.75 )*8 }}}
(1) {{{ 100 = 12.5*8 }}}
(1) {{{ 100 = 100 }}}
OK