# ABDUL WHILE DRIVING TO SCHOOL COMPUTES THE AVERAGE SPEED FOR HIS TRIP TO BE 20 KM/HOUR. ON HIS RETURN TRIP ALONG THE SAME ROUTE , THERE IS LESS TRAFFIC AND THE AVERAGE SPEED IS 30 KM/HOUR. WHAT IS THE AVERAGE SPEED FOR ABDUL'S TRIP?

Let the distance of the school from Abdu;l's home to school be s km

Let the time from home to school be t1

Let the time between return journey be t2

Therefore Average Speed = s / t1 = 20 km /hr so t1 = s / 20 hrs.

and similarly s / t2 = 30 km / hr so t2 = s / 30 hrs.

Total distance covered is s + s = 2s km.

Total time =(s / 20 + s/ 30 ) hrs

2s / s( 1 / 20 + 1 / 30) h

2 * 20 * 20 / 30 + 20

= 2 * 20 * 20 * 30 / 50

= 24 km /hr.

The average speed is 24 km .hr

• 67
for answer use 2ab/a+b formula where
• -20
aeruytiki;
• -22

Strategy: We need to calculate the time taken in each of the trip. After that, we can calculate the average speed.

Let the distance of the school = s km

Let time to reach the school in first trip = t1

Let time to reach the school in second trip = t2

We know that average speed `=text{Total distance}/text{time taken}`

∴ Average speed in first trip `=s/t_1`

`=>20\ km//h = s/t_1`

`=>t_1 = s/20 h`

∴ Average speed in second trip `=s/t_2`

`=>30\ km\\h = s/t_2`

`=>t_2 = s/30 h`

Now total time `(t_1+t_2)=s/20 +s/30`

`=>(t_1+t_2) = (3s+2s)/60 h`

`=>(t_1+t_2) =(5s)/60 h=s/12 h`

Now, Average in both of the trips `=text{Total distance covered}/text{Total time taken}`

`= (2s)/(s//12) \ km//h`

`=(2sxx12)/s \ km//h =24\ km//h`

Therefore, average speed of Adbul = 24 km/h

• -12 • 7
wsedrcfvtgbjmijijmkjjmi

Thumzz up
• -3
25km/hr is the AVG velocity for his trip
• -4
Barbie • 0
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