Common Causes of Mistakes in First Grade Addition and Subtraction
Mixing up signs (operations)
The very first thing that students need to pay attention to is the operation that they will be using when working on a Math problem. Most kids look at the numbers and start working on them without realizing that they are doing the complete opposite of the operation that they are supposed to be using. A great technique that most teachers use is to make students circle the operation that is shown in the equation (including word problems) before working on the Math problem.
Switching Place Values (reading numbers backwards)
Place value is a very important skill that students need to master before being able to solve addition and subtraction problems. They need to know the difference between the ones and the tens place values. Reversing these numbers is a simple mistake that they commonly make. Adding 1 and 19 could sometimes make students give an incorrect answer of 92 because they reversed 19 to 91 instead of answering 20. The same way when they are subtracting 1 from 19 and they will give an answer of 90. One technique that teachers use is having students underline the tens place in a number so that they know the higher value number before adding or subtracting.
Non-mastery of numbers 1 to 20
For grades KInder and 1st, the numbers 1 to 20 can already be a difficult set of numbers to master. Some students would sometimes have difficulty memorizing the numbers 1 to 10. It gets even more difficult for the numbers 11 to 20 because of the unusual pattern that numbers 11 and 12 have before reaching the teen numbers (13-19). Some teachers joke about making the numbers 11 and 12 into eleventeen and twelveteen in order to make them all uniform.
