Search Results For “doubling and halving to 20”

Rounding the lengths of bridges and rivers, or even birds' wingspans.

Practise finding pairs of multiples of 5 that total 100. There are only about ten pairs and if possible they should be learnt.

Help with adding whole tens and whole hundreds ?in your head?.

You may have seen tables' grids: these are addition grids and work in just the same way, adding rather than multiplying.

Adding 9 or 11 to 3-digit numbers by adding 10 and adjusting.

More practice at adding the nearest whole ten and adjusting, as well as looking at addition patterns.

Adding several numbers. A useful tip is to look for pairs of numbers that make 10 and do that part of the sum first.

Several ways to investigate the relationship between addition and subtraction.

More adding multiples of 10 to 2-digit and 3-digit numbers. The units remain the same in these questions.

Taking 15, 16, 17 or 18 from 2-digit numbers. The easiest way of doing this is by taking a whole ten and adjusting.

Finding the difference between two numbers as well as making subtraction number sentences from the numbers given.

Remember that subtractions can also be done by subtracting the nearest whole ten and adjusting.