Question

A bicycle wheel makes 5000 revolutions in moving 11km. Find diameter of the wheel.
$(A)$ 110cm
$(B)$ 60cm
$(C)$ 220cm
$(D)$ 70cm.

Answer 1

Hint: This question can be solved by using a unitary method. Here we need to consider the circumference of the circle formed and then we need to find the radius and then with the help of radius we will get the diameter that is twice the radius. Doing this will solve your problem and will give you the right answer.

Complete step-by-step answer:
In this question we have to find the diameter of the wheel of the bicycle,
Now using unitary method,
Distance travelled in one revolution is $2\pi r$ because in one revolution one circle is completed and we know the circumference of the circle is $2\pi r$.
Therefore distance travelled in 5000 revolution=$5000 \times 2\pi r$
Now, it is given to us that bicycle wheel makes 5000 revolution is moving 11km,
Therefore we can say that,
$ \Rightarrow 11km = 11 \times 1000 \times 100m = 5000 \times 2\pi r$
On putting $\pi = 3.14$ and hence on solving, we have
r=35cm
Now we all know that, Diameter=2r=$2 \times 35 = 70cm$

So, the correct answer is “Option D”.

Note: In this type of question we have to find the diameter and for that first of all we have to compare the distance given and travelled in 5000 revolution and hence on comparing we can find the value of radius and later on with the help of that we can find the diameter. Knowing this will solve your problem and will give you the right answer.