Math
posted by Da S on .
Mrs Leong took 1 hour to drive 1/5 of a journey from village R to village S.she drove the remaining 180km in 4hr. A) what was Mrs Leong's speed for the first part of the journey? B) how long did she take to travel the whole journey? C) find Mrs Leong's average speed for the whole journey

let the total distance be x km
her speed for first part = (1/5)x/1 km/h = x/5 km/h
speed for second part = 180/4 = 45 mph
remaining distance = x  (1)(x/5) = 4x/5
so, 4(45) = 4x/5
180 = 4x/5
4x = 900
x = 225
the total trip was 225 km
her speed in the first part = x/5 = 225/5 = 45 km/h
the whole trip took 5 hrs
average speed for whole trip was 225/5 = 45 km/h
check:
whole trip = 225 km
first part = 225180 = 45 km
1/5 of 225 = 45 km, check!
speed = 45/1 = 45 km/h , check!
second part of trip = 180 km
speed = 180/4 = 45 km/h
total time = 1 + 4 = 5 hrs/, check!
average speed for whole trip = 225/5 = 45 km/h