Question 973026
Let {{{ s }}} = his normal speed in km/hr
Let {{{ d }}} = distance from A to B in km
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Traveling at normal speed:
(1) {{{ d = s*5 }}}
Traveling at faster speed:
(2) {{{ d = ( s + 4 )*( 5 - .5 ) }}}
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(2) {{{ d = ( s + 4 )*4.5 }}}
(2) {{{ d = 4.5s + 18 }}}
Substitute (1) into (2)
(2) {{{ 5s = 4.5s + 18 }}}
(2) {{{ .5s = 18 }}}
(2) {{{ s = 36 }}}
His normal speed is 36 km/hr
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check:
(1) {{{ d = s*5 }}}
(1) {{{ d = 36*5 }}}
(1) {{{ d = 180 }}} km
and
(2) {{{ d = ( s + 4 )*4.5 }}}
(2) {{{ d = 40*4.5 }}}
(2) {{{ d = 180 }}} km
OK