Addition Within 20 Error Detective

Answer Key - Grade 1 Math Worksheet

Circle the answer, or write the answer on the line.

1. 1.

   A student wrote 7 + 10 = 17. Is it correct?

   • no
   • yes
2. 2.

   A student wrote 9 + 4 = 15. That is a mistake. What should it be?

   13
3. 3.

   Only one of these addition facts has a mistake. Which one?

   • 15 + 3 = 18
   • 6 + 8 = 14
   • 12 + 4 = 17
   • 6 + 5 = 11
4. 4.

   A student wrote 12 + 3 = 14. Is it correct?

   • no
   • yes
5. 5.

   A student wrote 2 + 11 = 14. That is a mistake. What should it be?

   13
6. 6.

   Only one of these addition facts has a mistake. Which one?

   • 2 + 14 = 16
   • 15 + 2 = 17
   • 6 + 4 = 9
   • 2 + 6 = 8
7. 7.

   A student wrote 6 + 2 = 8. Is it correct?

   • no
   • yes
8. 8.

   A student wrote 14 + 2 = 15. That is a mistake. What should it be?

   16
9. 9.

   Only one of these addition facts has a mistake. Which one?

   • 11 + 2 = 13
   • 11 + 7 = 19
   • 13 + 2 = 15
   • 2 + 8 = 10
10. 10.

    A student wrote 8 + 6 = 16. Is it correct?

    • no
    • yes