A person can drive from city A to city B at a certain rate of speed in 6 hours. If she decreases her speed by 10 mph, she can make the trip in 8 hours. How far is it from city A to city B?
first speed --- x mph
slower speed --- x-10 mph
case1 : distance = 6x miles
case2: distance = 8(x-10) miles
8(x-10) = 6x
2x = 80
x = 40
distance = 6x = 6(40) = 240 miles
check:
8(40-10) is also 240