Question

An aeroplane flies 200km with a uniform speed of 300km/h and then another 200km with a uniform speed of 240km/h. calculate the average speed of the aeroplane.​

Answer 1

Given :-

• An aeroplane flies 200km with a uniform speed of 300km/h and then another 200km with a uniform speed of 240km/h.

To find :-

• Average speed of aeroplane

Solution :-

• In first case

An aeroplane flies 200km with a uniform speed of 300km/h

• Distance (D1) = 200km
• Speed = 300km/h
• time (t1) = ?

As we know that

→ Speed = Distance/time

→ Time = Distance/speed

→ t1 = 200/300

→ t1 = 2/3 h = 0.6 h

• In second case

Another 200km with a uniform speed of 240km/h.

• Distance (D2) = 200km
• Speed = 240
• time (t3) = ?

→ Time = Distance/speed

→ t1 = 200/240

→ t1 = 20/24

→ t1 = 5/6 h = 0.8 h

Now,

→ Average speed = Total distance travelled/total time

→ Average speed = D1 + D2/t1 + t2

→ Average speed = 200 + 200/0.6 + 0.8

→ Average speed = 400/1.4

→ Average speed = 285.7 km/h

• Average speed in m/s

→ Average speed = 285.7 × 5/18

→ Average speed = 79.36 m/s

Answer 2

$\large\underline{\underline{\mathfrak{\color{lime}{Given :-}}}}$

• An aeroplane flies 200km .

• a uniform speed of 300km/h .

• then another 200km .

• a uniform speed of 240km/h.

$\large\underline{\underline{\mathfrak{\color{blue}{To \: Find :-}}}}$

• the average speed of the aeroplane.

$\large\underline{\underline{\mathfrak{\color{red}{Solution :-}}}}$

total distance = 200 + 200

total distance = 400 km

time taken for first 200 km

$\sf \to \: \frac{200}{300} \\\\ \sf \to \: \frac{2}{3}$

time taken for second 200 km

$\sf \to \: \frac{200}{240} \\\\ \sf \to \: \frac{5}{6}$

total time

$\sf \to \: \frac{2}{3}+\: \frac{5}{6} \\\\ \sf \to \: \frac{9}{6}\\\\\sf\to 1.5$

$\sf average \: speed \: = \frac{total \: distance}{total \: time}$

$\sf \to \: \frac{400}{1.5} \\ \\ \sf \to \: \frac{800}{3} \\ \\ \sf \to \red{ 266.67kmph} \:$