Question 550098
You need 1 equation for the car and 1 for the plane
Let {{{s}}} = the speed of the car
Let {{{t}}} = time for the car to travel {{{ 960 }}} km
given:
for the car:
(1) {{{ 960 = s*t }}}
for the plane:
(2) {{{ 960 = 3s*( t - 8 ) }}}
-------------------
(2) {{{ 960 = 3s*t - 24s }}}
Substitute (1) into (2)
(2) {{{ 960 = 3*960 - 24s }}}
(2) {{{ 960 = 2880 - 24s }}}
(2) {{{ 24s = 2880 - 960 }}}
(2) {{{ 24s = 1920 }}}
(2) {{{ s = 80 }}}
{{{ 3s = 240 }}}
The speed of the plane is 240 km/hr
The speed of the car is 80 km/hr
check answer:
(1) {{{ 960 = s*t }}}
(1) {{{ 960 = 80t }}}
(1) {{{ t = 960/80 }}}
(1) {{{ t = 12 }}} hrs
---------------
(2) {{{ 960 = 3s*( t - 8 ) }}}
(2) {{{ 960 = 240t - 240*8 }}}
(2) {{{ 960 = 240t - 1920 }}}
(2) {{{ 240t = 1920 + 960 }}}
(2) {{{ t = 2880 / 240 }}}
(2) {{{ t = 12 }}} hrs
OK