Question 545052
Let the distance your sister travels = {{{d}}}
Let her speed = s
Your distance is {{{ 436 - d }}}
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Sister's equation:
(1) {{{ d = 4s }}}
Your equation:
(2) {{{ 436 - d = 4*( s + 15 ) }}}
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(2) {{{ 436 - d = 4s + 60 }}}
Substitute (1) into (2)
(2) {{{ 436 - 4s = 4s + 60 }}}
(2) {{{ 8s = 436 - 60 }}}
(2) {{{ 8s = 376 }}}
(2) {{{ s = 47 }}}
your speed is
{{{ s + 15 = 47 + 15 }}}
{{{ s + 15 = 62 }}}
Your speed is 62 mi/hr
check:
(2) {{{ 436 - d = 4*( s + 15 ) }}}
(2) {{{ 436 - d = 4*( 47 + 15 ) }}}
(2) {{{ d = 436 - 4*62 }}}
(2) {{{ d = 436 - 248 }}}
(2) {{{ d = 188 }}}
and
(1) {{{ d = 4s }}}
(1) {{{ d = 4*47 }}}
(1) {{{ d = 188 }}}
OK