Question

Dariella walks xkm at 5km/h and then runs (x+4)km at 10km/h. Calculate average speed

Answer 1

average speed = total distance/total time taken

Dariella walks x km at 5km/h
time taken = distance/speed
so, time, t = x/5 hours

again, Dariella runs (x + 4)km at 10 km/h
so, time taken in this case , t' = (x + 4)/10 hours


now, total distance = x + x + 4 = (2x + 4) km
total time taken = t + t' = x/5 + (x + 4)/10 = (2x + 4)/10

so, average speed = (2x + 4)/(2x + 4)/10 = 10km/h

hence, average speed = 10km/h

Answer 2

Answer:

avg speed= (20x+40)/(3x+4) km/h

Step-by-step explanation:

time = distance/speed

time taken to walk= x/5

Time taken in running= (x+4)/10

total time elapsed = (x/5)+(x+4)/10

= (2x+x+4)/10= (3x+4)/10

total distance covered= x+ (x+4)= 2x+4

Avg speed= total distance covered/time elapsed=(2x+4)/(3x+4)/10

=(20x+40)/(3x+4)

Answer is (20x+40)/(3x+4) km/h