Question 752026
Let {{{ s }}} = Ernie's speed
{{{ s - 15 }}} = Bert's speed
Let {{{ t }}} = time in hours for both
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Ernie's equation:
(1) {{{ 225 = s*t }}}
Bert's speed:
(2) {{{ 150 = ( s-15 )*t }}}
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(2) {{{ 150 = s*t - 15t }}}
Substitute (1) into (2)
(2) {{{ 150 = 225 - 15t }}}
(2) {{{ 15t = 75 }}}
(2) {{{ t = 5 }}}
and
(1) {{{ 225 = s*5 }}}
(1) {{{ s = 45 }}}
and
{{{ s - 15 = 30 }}}
Bert's speed is 30 mi/hr
check:
(2) {{{ 150 = ( s-15 )*t }}}
(2) {{{ 150 = ( 45-15 )*5 }}}
(2) {{{ 150 = 150 }}}
OK