Question 601553
Let {{{ s }}} = the speed of the older model
Let {{{ t }}} = time in hours older model takes to travel 900 mi
and newer model takes to travel 1200 mi
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Equation for older model:
(1) {{{ 900 = s*t }}}
Equation for newer model:
(2) {{{ 1200 = ( s + 200 )*t }}}
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Substitute (1) into (2)
(2) {{{ 1200 = s*t + 200t }}}
(2) {{{ 1200 = 900 + 200t }}}
(2) {{{ 200t = 300 }}}
(2) {{{ t = 1.5 }}}
and, since
(1) {{{ 900 = s*1.5 }}}
(1) {{{ s = 900/1.5 }}}
(1) {{{ s = 600 }}}
The speed of the older model is 600 mi/hr
check:
(2) {{{ 1200 = ( s + 200 )*t }}}
(2) {{{ 1200 = ( 600 + 200 )*t }}}
(2) {{{ t = 1200/800 }}}
(2) {{{ t = 1.5 }}}
OK