How do you do front-end estimation for subtraction? I need the answer as fast as possible!

Well i think this is it but I am not really sure what your teacher is after 

$$\\2310 - 1293\\
\approx 2000-1000\\
\approx 1000\\\\\\
987-213\\
\aaprox 1000-200\\
\approx 800$$

Okay. To do front-end subtraction you subtract the 2 highest value places. And then fill the rest of the places with zeros.

For example:

$${\mathtt{2\,310}}{\mathtt{\,-\,}}{\mathtt{1\,293}}$$

We take the 2 highest value places, which are 23 and 12

$$\mathbf{23}10-\mathbf{12}93$$

Now we subtract these two numbers.

$${\mathtt{23}}{\mathtt{\,-\,}}{\mathtt{12}} = {\mathtt{11}}$$

How fill the other place values with zeros:

$$\mathrm{11}\textit{00}$$

There we go.

So, can you help me with this one?

 8.75-5.67?

Okay. To do front-end subtraction you subtract the 2 highest value places. And then fill the rest of the places with zeros.

$$8.75-5.67$$

We take the 2 highest value places, which are 8.7 and 5.6

$$\mathbf{8.7}5-\mathbf{5.6}7$$

Now we subtract these two numbers.

$${\mathtt{8.7}}{\mathtt{\,-\,}}{\mathtt{5.6}} = {\frac{{\mathtt{31}}}{{\mathtt{10}}}} = {\mathtt{3.1}}$$

How fill the other place values with zeros:

$$\mathrm{3.1}\textit{0}$$

There we go.

So, do I always use the first 2 digits???

Yer. Well.. That's what I know of. I always just use 2 digits. 

Thank you!

I don't think so Takahiro,

I think Dragon is supposed to ROUND to 2 significant figures - not just truncate!

Really, how?

Thank you Melody.