Question 43188
DISTANCE = RATE * TIME
TIME = DISTANCE/RATE
TIME OF FIRST CAR - TIME OF SECOND CAR = 0
DISTANCE/RATE OF FIRST CAR - DISTANCE/RATE OF SECOND CAR = 0
{{{60/r - 90/(r + 10) = 0}}}
{{{(60r(r+10))/r - (90r(r+10))/(r + 10) = 0r(r+10)}}}
{{{60(r+10) - 90r = 0}}}
{{{60r + 600 - 90r = 0}}}
{{{-30r = -600}}}
{{{r = 20}}}