Question 737833
I will say that usually her motion equation is
(1) {{{ d = r*t }}}
When she walks at 3/4 her usual speed,
her equation is:
(2) {{{ d = (3/4)*r*( t + 2.5 ) }}}
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The only units given are hours
I can say {{{ d = 1 }}} unit, miles or what ever, so
(1) {{{ 1 = r*t }}}
(2) {{{ 1 = (3/4)*r*( t + 2.5 ) }}}
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(2) {{{ 1 = (3/4)*( r*t + 2.5r ) }}}
Substitute (1) into (2)
(2) {{{ 1 = (3/4)*( 1 + 2.5r ) }}}
(2) {{{ 1 = 3/4 + (3/4)*(5/2)*r }}}
(2) {{{ 8 = 6 + 15r }}}
(2) {{{ 15r = 2 }}}
(2) {{{ r = 2/15 }}}
and, since
(1) {{{ 1 = r*t }}}
(1) {{{ 1 = (2/15)*t }}}
(1) {{{ t = 15/2 }}}
(1) {{{ t = 7.5 }}}
Her usual time is 7.5 hrs
check:
(2) {{{ 1 = (3/4)*r*( t + 2.5 ) }}}
(2) {{{ 1 = (3/4)*(2/15)*( 7.5 + 2.5 ) }}}
(2) {{{ 1 = (6/60)*10 }}}
(2) {{{ 1 = 1 }}}
Hope I got it