It took Candice 35mins. walk from his house to the park 20km away. It took her just 25mins. walk back home. What is his average speed

Question

I used in here the formula: Speed=distance/time.

Correct me if im wrong, I got 20kph as my answer. I'm quite unsure with it. Can you please show me the correct equation/solution in this word problem. Thanks a lot!

Answer 1

 

d=r*t

total distance=rate*total time

40=r*1  (35+25=60 min=1 hour)

r=40 kph answer

 

another solution more difficult..

20=r*(35/60)

20=r*(25/60)

 

20=r*(7/12)

20*(12/7)=r

r=34 2/7 kph

 

20=r*(5/12)

20*(12/5)=r

r=48 kph

 

now find the harmonic mean...

2*(34 2/7)*(48)/[(34 2/7)+(48)]=40 again after doing the arithmetic