Question

The wheels of a car are of diameter 80 cm each. How many complete revolutions does
each wheel make in 10 minutes when the car is travelling at a speed of 66 km per hour?​

Answer 1

The wheels of car of diameter = 80 cm

Radius of wheel = Diameter/2 = 80/2 = 40 cm

Circumference of circle = 2πr

⇒ 2 × 22/7 × 40

⇒ 80 × 22/7

We have to find the number of revolutions taken by each wheel in 10 min.

We know that, 1 hour = 60 min

So, 10 min = 1/6 hrs.

Now,

Distance = Speed × time

Given that, car is travelling at a speed of 66 km/hr.

⇒ 66 × 1/6

⇒ 11 km

Therefore, distance covered by car in 10 min is 11 km.

We also know that,

1 km = 1000 m

1 m = 100 cm

So, 1 km = 100000 cm (1000 × 100)

Therefore, 11 km = 1100000 cm

Distance covered by car is 1100000 cm.

Now,

Number of revolutions = Distance covered by car/Circumference of car

⇒ 1100000/(80 × 22/7)

⇒ (1100000 × 7)/(80 × 22)

⇒ 4375

Therefore, total number of revolutions taken by each wheel in 10 min is 4375 when the car is travelling at a speed of 66 km/hr.

Answer 2

Given :---

• Diameter of Car of wheel = 80cm.
• Time given = 10 minutes .
• Speed = 66km/h .

To Find :---

• How many revolutions does each wheel make ?

Formula and Concept used :---

• Each wheel cover distance Equal to its Circumference while covering one Revolution.
• Circumference of wheel = 2πr, where r is Diameter/2 .
• 1 hour = 60 minutes .
• 1 km = 1000m.
• 1m = 100cm.

Solution :---

From above Told formula we have now,

→ radius of wheel = 80/2 = 40cm

So,

→ Circumference of wheel = 2πr = 2*(22/7)*40 = (1760/7)cm.

So, we can say that the wheel covers (1760/7)cm distance in one Revolution.. _____________________________

Now,

Speed of Car is given 66km/h.

That means ,

→ in 60 min car cover = 66*1000*100 cm.

→ in 1 min car cover = (66*1000*100)/60 cm .

→ in 10 min car will cover = (66*1000*100)/6 cm = 1100000 cm.

_____________________________

Now,

→ (1760/7) cm distance covers in = 1 revolution by the wheel .

→ 1 cm distance covers in = 1/(1760/7) = (7/1760) revolution .

→ 1100000 cm distance will be cover in = (7*1100000)/1760 = 4375 revolutions..

Hence, Each wheel will Complete 4375 Revolutions in 10minutes..