Question

Express the following as cm by using the decimals:
30mm

Answer 1

Hint: We solve this problem by using the conversions of length from millimetres to centimetres. The conversion of length from mm to cm is given as
\[1cm=10mm\]
By using this conversion we convert the given length of 30mm into cm.

Complete step by step answer:
We are given that the length to be converted to cm as 30mm.
Let us assume that the given length as
\[\Rightarrow l=30mm........equation(i)\]
Now, we know that the conversion of length from mm to cm is given as
\[1cm=10mm\]
Here, we can see that the above conversion can also be written in the form
\[\Rightarrow 1mm=\dfrac{1}{10}cm\]
Now, let us take the equation (i) and by substituting the value of 1mm then we get
\[\begin{align}
  & \Rightarrow l=30\times \dfrac{1}{10}cm \\
 & \Rightarrow l=\dfrac{3}{1}cm \\
 & \Rightarrow l=3cm \\
\end{align}\]
We are asked to represent the 30mm length in cm by using the decimals.
Here, we can see that there is no possibility of getting the decimal form because we can see that there is no division.
We know that keeping zeros after the decimal point will have no change.
So, by converting the above equation into decimals we get
\[\Rightarrow l=3.0cm\]

Therefore, we can conclude that 30mm is equal to 3.0cm.

Note: Students may miss the point of representing the answer in decimal form.
We get the value of 30mm in cm as
\[\Rightarrow l=3cm\]
Here, there is no possibility of getting the decimal form because we can see that there is no division.
But, we are asked to represent the given length in decimal form.
We know that that keeping zeros after the decimal point will have no change.
So the given length can be represented as
\[\Rightarrow l=3.0cm\]
This gives the final answer.
But students may leave the solution at
\[\Rightarrow l=3cm\]
This will not give us the complete answer according to the question.