A cycle road consists of a series of uphill and downhill sections. Lina averaged 20km/hr uphill and 40km/hr downhill. If she completed 35km in 1.3 hours, determine the length of the downhill section?

Answer 1

Another way

time = distance/rate

Let x be uphill distance and y be the down hill distance

x+y=35

x = 35-y

x/20 + y/40 = 1.3

(35-y)/20 +y/40 = 1.3

2(35-y)/40 +y/40 = 1.3

70 - 2y + y = 40(1.3) = 52

-y = 70-52 = -18

y = 18 km

Answer 2

Let x = time going uphill

Then 1.3 - x = time going downhill

So 20x = the distance she rode uphill

And 40 ( 1.3 - x) = the distance she rode downhill

20x + 40 (1.3 - x) = 35

20x + 52 - 40x = 35

-20x + 52 = 35

-20x = -17

x = 0.85

1.3 - 0.85 = 0.45 hours going downhill

Now we can answer the question

40 km/hr times 0.45 hours = 18 KM