Question 1147215
Let {{{ s }}} = the jet's speed in mi/hr
The jet flew for {{{ 5s }}} miles until the passenger plane took off
( This is the jet's head start )
Let {{{ d }}} = the distance in miles the passenger plane flew
{{{ 5670 - d }}} = the distance in miles the jet flew
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Equation for the passenger plane
(1) {{{ d = 315*4 }}}
Equation for the jet
(2) {{{ 5670 - d - 5s = s*4 }}}
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(1) {{{ d = 1260 }}}
Plug (1) into (2)
(2) {{{ 5670 - 1260 - 5s = 4s }}}
(2) {{{ 9s = 4410 }}}
(2) {{{ s = 490 }}}
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The jet's speed is 490 mi/hr
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check:
(1) {{{ d = 1260 }}}
(2) {{{ 5670 - d - 5s = s*4 }}}
(2) {{{ 5670 - 1260 - 5*490 = 490*4 }}}
(2) {{{ 4410 - 2450 = 1960 }}}
(2) {{{ 1960 = 1960 }}}
OK
check the math & get another opinion if needed