Question

a boy covers 10km at a speed of 5kmph, 30km at a speed of 7kmph, 20km at a speed of 15kmph. find the average speed.

Answer 1

Answer:

I don't know your anwer because your question is not clear

Answer 2

Average speed = 21kmph

Explanation:-

We know that,

Average speed :-

$\frac{total \: distance}{total \: time}$

So, first case :-

D1 = 10km

S1 = 5kmph

T1=> 10/5= 2h

second case :-

D2 = 30km

S2 = 7kmph

T2 = 30/7h

third case:-

D3 = 20km

S3 = 15kmph

T3 => 20/15 = 4/3h

So, Total Distance => D1+D2+D3

=>10+30+20= 60km

And, Total time =>T1+T2+T3

=>2+30/7+4/3

=>(42+90+28)/21

=>160/21 h

Now, applying the formula :-

average speed=>60/(160/21)=60x21/160 =21

So, average speed is 21kmph

I hope you find my answer helpful.