<p>For example, calculate the sum of 367 + 584 by using partial sum addition. You can then use the answer to verify the result from your partial sums addition.</p>
<p>Round the hundreds down to the nearest unit and then add the hundreds together. For example, 300 + 500 = 800.</p>
<p>Round the tens down to the nearest unit, and then add the two numbers together. For example, 60 + 80 = 140.</p>
<p>Add the units together. For example, 7 + 4 = 11.</p>
<p>To create the final total, add the numbers for the hundreds, tens and units together. For example, 800 + 140 + 11 = 951.
Because you only add round numbers of hundreds and tens, you can do the calculation quickly in your head.</p>