Adding the Doubles Pair First and Then the Third Number

You will meet this idea in ordinary days. People lean on what they know cold. A carpenter who knows his common lengths by heart works faster than one who measures everything twice. This is worth learning because using facts you already know cold makes new problems shorter.

Watch for it today, and when you spot it, tell someone what you noticed and how you knew. Watch this carefully, friend. Doubles are two of the same number, like 4 plus 4. Most people learn doubles quickly, so use them.

In 4 plus 4 plus 6, add the double first to get eight, then eight plus six is fourteen. Scan for a matching pair the same way you scan for a ten pair. If you find both a double and a ten pair, use whichever is easier for you. There is no single right order.

Here is how to choose. If you spot both a ten pair and a doubles pair, use whichever answer arrives in your head faster. There is no prize for using the fancier method. The best strategy is the one you can do correctly without slowing down. If you get stuck, use your fingers or counters. Good mathematicians use tools.