Answer: Jacob ran for half an hour, and walked for the remaining half an hour. 15 km/hr x 0.5 hr = 7.5 km running, and 5km/ hr x 0.5 hr=2.5 km walking
Explanation:
Let x hours be the time Jacob ran, and therefore for 1-x hours he walked.
time x speed= distance
we get, 15x + 5*(1-x)=10
15x+5-5x=10,
10x=5,
x=0.5 hours.
Average speed was 10km/h.
HOPE THIS HELPS.