When writing down sums, separate the numbers into ones, tens, hundreds and thousands. List the numbers in a column and always start adding with the ones first.

• Estimate first and check afterwards - it's a good idea to estimate a rough answer first and then check your actual answer.
• Order doesn't matter - remember that 345 + 129 is the same as 129 + 345.
• Key words - look out for these words in problems: total, sum, altogether, more. They all indicate an addition calculation.