If your child is learning multiplication facts the 7s times table will probably be one of the last they learn. That’s because the 7s times table can be the most challenging. Why? Because 7 is a prime number. You might be thinking that 3 and 5 are also prime so why is the 7 times table more difficult? Let me explain.

A prime number is a number whose factors (the numbers being multiplied) are only itself and one. In other words, the only numbers you can multiply to get 7 are 7 and 1 or 1 and 7. The same is true for 3. Because there are less fact families for prime numbers, there are more facts to learn. By contrast, composite numbers have more factors so there are less facts to learn. Take the number 4, for example. You can multiply 2 and 2 to get 4, along with 1 and 4. 

While 3 and 5 are prime numbers, the times tables for these numbers are relatively easy for students to learn because of obvious patterns in the products and quicker addition.

For the 5s times table, students know that each product (the answer to a multiplication problem) must end in 0 or 5, and this alternates back and forth throughout the times table. Even young students can learn how to count by 5s and later connect this to multiplication.

Similarly, the 3s are relatively easy to learn despite 3 being a prime number. Once students learn the connection between multiplication and repeated addition, they can easily skip count by 3s to find the desired product. 

For example, a student trying to solve 3 x 4 might know 3 x 3 is 9. The student can then quickly add another “group of” 3 to 9 and see that 3 x 4 = 12. While this strategy also works with the 7s times table, adding 7 to a number is typically more difficult.

Let’s say a student is trying to work out 7 x 5. The student might remember that 7 x 4 is 28. Then, the student can add another “group of” 7 to 28. While this will still lead to the correct answer of 35, it is usually more challenging for students to quickly add 7 to a number than it is to add 3 because it’s larger.