Find the value of $0.4\div 2.$

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Hint: Transform 0.4 into fraction by multiplying and dividing by 10. Then divide the result by 2, or you can even multiply by $\dfrac{1}{2}$. This is a very easy and simple question to solve.

We have to find the value of,
$0.4\div 2$
We can write the above equation as,
Now, consider the numerator part, that is, 0.4.
First we will convert it into fractions.
To make it into a fraction, let us divide and multiply the numerator of the given expression by 10, so we get
$0.4=\left( \dfrac{0.4\times 10}{10} \right)............\left( 2 \right)$
What is $0.4\times 10$ now?
Remember, multiplying by 10 just shifts decimal place to right.
$\therefore 0.4\times 10=4.0...........\left( 3 \right)$
Now substituting value from equation (3) into equation (2), we get
This is the fraction form of 0.4.
Now, consider the expression (1), an substituting the fraction form of 0.4 in it,, we get
We know that dividing by any number is nothing but multiplying by its inverse, so the above expression can be written as,
$\dfrac{0.4}{2}=\dfrac{4}{10}\times \dfrac{1}{2}$
Now we know, $4=2\times 2$, so the above expression can be written as,
$\dfrac{0.4}{2}=\dfrac{2\times 2}{10\times 2}$
Cancelling the like terms, we get
Now we know dividing any number by 10, then the decimal shift one point to the left, so the above expression can be written as,
Hence this is the required answer.

Note: Another method is to count the decimal places, for 0.4 that is one. Ignore decimal and divide 4 by 2, we get 2. Now, apply the one decimal place we get 0.2
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