Efficient Subtraction

he 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.