Question

a car moves with a speed of 30 km per hour for half an hour ,25 kilometre per hour for 1 hour and 40 kilometre per hour for 2 hours calculate the average speed of the car.....
plz ans. i will mark u brainlist ( answer step by step)​

Answer 1

$\bigstar$ Given :

A car moves with a speed of 30 km/hour for half an hour ,25 km/hour for 1 hour and 40 km/h for 2 hours

$\bigstar$ To Find :

The average speed of the car

$\bigstar$ Concept Used :

Average Speed :

Average Speed is defined as the total distance covered per total time .

$\bigstar$ Solution :

Case - 1 :  For 1st half an hour

$\bf Speed, S_1=30\ km/h\\\\\bf Time,T_1=0.5\ h\\\\\bf Speed=\dfrac{Distance}{Time}\\\\\implies \bf D_1=S_1*T_1\\\\\implies \bf D_1=30*0.5\\\\\implies \bf D_1=15\ km$

Case - 2 : For 2nd hour

$\bf Speed,S_2=25\ km/h\\\\\bf Time,T_2=1\ h\\\\\implies \bf D_2=S_2*T_2\\\\\implies \bf D_2=25*1\\\\\implies \bf D_2=25\ km$

Case - 3 : For 3rd 2 hours

$\bf Speed,S_3=40\ km/h\\\\\bf Time,T_3=2\ h\\\\\implies \bf D_3=40*2\\\\\implies \bf D_3=80\ km$

Now ,

$\bf Total\ Distance,D=D_1+D_2+D_3\\\\\implies \bf D=15+25+80\\\\\implies \bf D=120\ km$

$\bf Total\ Time,T = T_1+T_2+T_3\\\\\implies \bf T=0.5+1+2\\\\\implies \bf T=3.5\ h$

So ,

$\bf Average\ Speed=\dfrac{Total\ Distance}{Total\ Time}\\\\\implies \bf Average\ Speed=\dfrac{D}{T}\\\\\implies \bf Average\ Speed=\dfrac{120}{3.5}\\\\\implies \bf Average\ Speed=34.28\ km/h$