*30 days worth of number strings geared to the third grade subtraction skills. Number Strings are research-based Number Talks that have shown to improve number sense and mathematical fluency. This resource can be used as a tier 1 daily routine or as intervention for older students. I have used this resource in grades 2-6 to improve number sense and operational accuracy. Can be used with other number sense routines to further enhance number sense! This can be a short unit OR used as intervention