Efficient Subtraction Core

The purpose of this worksheet is to encourage
children to make choices about which method is most appropriate
for a given calculation. Children can often become reliant on
formal written methods, so it is important to explicitly highlight
where mental strategies or less formal jottings can be more
efficient.
Children explore the concept of constant difference, where
adding or subtracting the same amount to/from both numbers
in a subtraction means that the difference remains the same,
for example 3,835 – 2,999 = 3,835 – 3,000 or 700 – 293 = 699 – 292.
This can help make potentially tricky subtractions with multiple
exchanges much simpler, sometimes even becoming calculations
that can be performed mentally.
Number lines can be used to support understanding of this concept.