Adding a column up

Make the computer add a column up, and watch the total correct itself the moment you change one of the numbers.

Here is the payoff, before any of the words: you put a total at the bottom of a column, and from then on, whenever you change one of the numbers above it, the total corrects itself. You never add anything up again.

There are three words people use for what is going on. Each of them means something perfectly ordinary.

Key points

• Put a total at the bottom of a column with one press.
• Say what =SUM(B2:B7) means in plain English.
• Change a number and know the total will look after itself.

What to remember

• Choose the empty box under the column, press Add up. The total stays right for ever afterwards.
• A total box holds an instruction, not a number. Leave it alone and it will stay right for years.

Try this

Type five numbers down a column in any spreadsheet, press the box underneath them, and find the Add up button — often a sigma, which looks like a capital E made of straight lines. Then change one of the five and watch the bottom.

Practice: Adding a column up. Your first lesson is free, with no account or card; the rest are part of a Lantern plan. Interactive lessons require JavaScript.

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