This spreadsheet provides Bar Model questions on addition and subtraction.
Each time you press F9, randomly generated numbers create a unique set of questions. The bars change with the questions to show the numbers involved in accurate proportions.
The main feature of this spreadsheet is that it allows you to modify the range of questions. All questions are set for a maximum sum of 100 but if you need a question sheet for pupils with a maximum sum of 30, simply change the values in two cells and print it out.