# Subtracting on paper

• Aug 1st 2008, 11:53 AM
spoosh
Subtracting on paper
Hi,

I have a test paper which I am going through but I am struggling on on question, below.

I am not permitted to use a calculator.

Although this would be simple to do in your head, I want to know how I could do it on paper:

30.00
0.86

The answer (yes I cheated, but won't on the actual test) is: 29.14, but I never get this answer when I try and work out this subtraction on paper.

Could someone explain the technique which I need to use to show it on paper?

Thank you.
• Aug 1st 2008, 12:35 PM
Quick
Hmm.

What is \$\displaystyle 3000 - 86\$?
• Aug 1st 2008, 01:30 PM
masters
Quote:

Originally Posted by spoosh
Hi,

I have a test paper which I am going through but I am struggling on on question, below.

I am not permitted to use a calculator.

Although this would be simple to do in your head, I want to know how I could do it on paper:

30.00
0.86

The answer (yes I cheated, but won't on the actual test) is: 29.14, but I never get this answer when I try and work out this subtraction on paper.

Could someone explain the technique which I need to use to show it on paper?

Thank you.

You might want to google a few sites like:

Cool math Lessons - How to Subtract Decimals (Subtraction)

Subtraction with Decimals

to look at a few examples.
• Aug 1st 2008, 05:14 PM
topsquark
Quote:

Originally Posted by spoosh
Hi,

I have a test paper which I am going through but I am struggling on on question, below.

I am not permitted to use a calculator.

Although this would be simple to do in your head, I want to know how I could do it on paper:

30.00
0.86

The answer (yes I cheated, but won't on the actual test) is: 29.14, but I never get this answer when I try and work out this subtraction on paper.

Could someone explain the technique which I need to use to show it on paper?

Thank you.

Quote:

Originally Posted by Quick
Hmm.

What is \$\displaystyle 3000 - 86\$?

This kind of post is the reason I think that calculators are introduced waaaay too early in the Mathematics curricula.

As quick suggests, write it out like a regular subtraction. Make sure that you put the decimals in line like this:
Code:

```  30.00   -0.86```
Now forget that the decimal point exists and subtract:
Code:

```  3000   - 86   2914```
Now put the decimal point back in:
Code:

```  30.00   -0.86   29.14```
-Dan