Question

A train travels 20 km at a uniform
speed of 60 Kmh^-1 and the heat 20km at a
uniform speed of 80 kmh^-1 Calculate
its average speed​

Answer 1

in travelling first 20 km the time taken is= distance/speed=20/60=1/3

and in travelling another 20 km time=20/80=1/4

therefore, total time=1/3+1/4=7/12

we know,

average speed=total distance/ total time

= (40*12)/7

= 68.57.

$itzDopeGirl$❣

Answer 2

Gɪᴠᴇɴ

Train travels 20 km at speed of 60 km/h

Train again travels 20 km at speed of 80 km/h

Tᴏ ꜰɪɴᴅ

Average speed of train

Sᴏʟᴜᴛɪᴏɴ

As we know that,

⇒ Time = Distance/Speed

Case ⓵ :

⇒ Time₁ = 20/60

⇒ Time₁ = 1/3 h

Case ⓶ :

⇒ Time₂ = 20/80

⇒ Time₂ = 1/4 h

Now we know that,

⇒ Average speed = Total distance/Total time

⇒ Average speed = (20 + 20)/(1/3 + 1/4)

⇒ Average speed = 40/[(4 + 3)/12]

⇒ Average speed = 40/(7/12)

⇒ Average speed = 40 × (12/7)

⇒ Average speed = 68.57 km/h

Tʜᴇʀᴇꜰᴏʀᴇ,

Average speed of train = 68.57 km/h