Know What Each Number Counts

You'll learnto tell whether a number counts a part or the whole, then report the quantity asked.

A ratio compares parts, and the first job is knowing whether a number counts a part or the whole; points leak in mixing part-to-part with part-to-whole, setting a rate upside down, and reporting the wrong quantity.

8 STEPS · 6 QUICK CHECKS · part or whole? · keep the rate right-side up · v2

parts · rates

Before you start

What you're looking at

A bar for dogs : cats = 3 : 5 — three tiles for dogs, five for cats, eight in all.

The question

Does each number in the ratio count a part or the whole — and what is the total?

Watch for

The tiles fill in; watch that both 3 and 5 are parts, so the whole is their sum — eight, not five.

What the symbols mean

Each tile is one part; the dog tiles and cat tiles are different colors, and the full bar is the whole — eight parts.

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