We climbed the pass at a speed of 2 km / h. and descended at a speed of 4 km / h What was the average speed

We climbed the pass at a speed of 2 km / h. and descended at a speed of 4 km / h What was the average speed along the way. If 3/4 of the total time was spent on the ascent

Given:
v1 = 2km / h,
v2 = 4km / h,
t1 = 3/4 * t;
Find: v -?
The average speed is equal to the ratio of the total distance traveled to the time spent:
v = s / t,
where
s = s1 + s2
and
t = t1 + t2;
Here
s1 = v1 * t1 = 3/4 * v1 * t;
s2 = v2 * t2;
find the time spent on the second part of the path:
t2 = t – t1 = 1/4 * t1;
s2 = 1/4 * v2 * t;
We get:
S = 3/4 * v1 * t + 1/4 * v2 * t = t * (3 * v1 + v2) / 4;
Find the average speed:
v = (3 * v1 + v2) / 4 = (6 + 4) / 4 = 2.5km / h.