Comprehensive Year 3 resources for adding and subtracting 100s, 10s, or 1s to/from 3-digit numbers, promoting flexible mental calculation, a core KS2 Maths objective. Activities build reasoning by requiring pupils to identify which digit is affected by the operation, supporting efficient calculation strategies. This crucial small step supports mastery of mental arithmetic and is vital for meeting national curriculum expectations. The CS Maths Scheme provides structured Base 10 and pictorial practice.