I mentioned in the previous blog entry and in another earlier post that I had found two websites which generated math worksheets. Even though I liked those resources, I still wanted my own math worksheet generator if I could create it without too much trouble. The solution that I came up with was to use a spreadsheet that contained formulas which generated random numbers.
The key to the worksheet is a four-cell block that is two columns wide by two rows tall. In the right-hand column, both the top and bottom cells have the following formula: =randbetween(1,12)
This formula will generate a random number between 1 and 12, inclusive. To generate a larger number, simply change the 12 to the desired number. This weekend we will start reviewing long addition and subtraction, so I’ll probably change the 12 to 1000 in order for my kids to get practice with more complex problems.
In the left-hand column, on the bottom row, you can put the order of operation if you want it to be the same for all of the problems on the page. For my daughters I wanted to mix addition and subtraction problems, but I wanted to make sure that if the number in the upper right cell was smaller than the number in the lower right cell that I didn’t use a minus sign because we weren’t working on negative numbers yet. The solution involved the use of two formulas.
In the upper left-hand cell, the formula was “=rand()” without the quotation marks. This generated a random number between 0 and 1 that could be used to randomly determine whether to use a “+” or a “-“. I didn’t want this number to be visible, so I changed the font to white in the upper left cell.
The first group of cells on my worksheet that have this four cell group are B3:C4. In the lower left cell (B4), the formula I used was: IF(C3>=C4,IF(B3>0.5,”-“,”+”),”+”)
The quotation marks in the formula are important (at least they are in LibreOffice), and should be included.
The first “IF” tests to see whether the number in the upper right cell is greater than or equal to the number in the lower right cell. This needs to be done in order to avoid a subtraction problem that would have a negative number for a solution (which is important for us at this time, but may not be in the future). If the number in the upper right cell is greater than or equal to the value in the lower right cell, then either a “+” or a “-” can be used, otherwise only a “+”. The second “IF” tests whether or not the value of the hidden formula in the upper left cell (B3) is greater than “0.5”. If it is, then the lower left cell (B3) will show a “-“; if the value in the upper left cell is less than “0.5” then the lower left cell will show a “+”.
The four-cell group is then copied and pasted as many times as desired throughout the worksheet. Currently the worksheets I’m generating have 36 problems, 6 rows of six problems. Once the worksheet is saved there is no need to edit any of the formulas unless I want to change the size of the numbers in the problems.
The good thing about the random number formulas is that each time I open the worksheet they generate new numbers, so that the likelihood of having the exact same worksheet twice is very remote. In LibreOffice, I can also go to File -> Reload and the worksheet will reopen, causing the formulas to be recalculated. In this way I can print a bunch of different worksheets in one sitting.
I’ve included several versions in case they might be of use to anyone. The pdf version is static, and won’t generate new worksheets. Downloading it multiple times will not generate new worksheets either. The other versions can be saved to your computer and used for generating your own worksheets, should you care to do so. The Excel version was saved using LibreOffice and has not been tested in Excel, but it should work without any issues. If not, then the formulas can always be edited as per the instructions above, and then be recopied throughout the worksheet (or be changed using Find and Replace).
pdf version: Addition and Subtraction Worksheet
LibreOffice template: Addition and Subtraction Worksheet
Microsoft Excel version: Addition and Subtraction Worksheet