Question 633581
Let {{{ c }}} = the speed of the current
Boat's speed going upstream = {{{ 25 - c }}}
Boat's speed going downstream = {{{ 25 + c }}}
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going upstream:
(1) {{{ 60 = ( 25 - c )*2t }}}
going downstream:
(2) {{{ 60 = ( 25 + c )*t }}}
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(2) {{{ 60 = 25t + c*t }}}
(2) {{{ c*t = 60 - 25t }}}
(2) {{{ c = 60/t - 25 }}}
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Substitute (2) into (1)
(1) {{{ 60 = ( 25 - 60/t + 25 )*2t }}}
(1) {{{ 60 = 50t - 120 + 50t }}}
(1) {{{ 100t = 180 }}}
(1) {{{ t = 1.8 }}} hrs
and
(2) {{{ 60 = ( 25 + c )*1.8 }}}
(2) {{{ 60 = 45 + 1.8c }}}
(2) {{{ 1.8c = 15 }}}
(2) {{{ c = 8.333 }}} mi/hr
check answer:
(1) {{{ 60 = ( 25 - 8.333 )*2t }}}
(1) {{{ 60 = 16.666*2t }}}
(1) {{{ t = 60 / 33.333 }}}
(1) {{{ t = 1.8 }}}
and
(2) {{{ 60 = ( 25 + 8.333 )*1.8 }}}
(2) {{{ 60 = 45 + 15 }}}
(2) {{{ 60 = 60 }}}
OK