Teacher brief

Comparing Tens and Ones

Grade 2 · Lesson 3 · Dimensions 2A, pages 10–13

What this lesson is

To compare two-digit numbers, compare the TENS first. Only if the tens are equal do the ones decide it.

Why it is built this way

The warm-up reaches back to Counting by Tens or Ones. That is not a starter to settle the class — it is retrieval, and retrieval of the immediately preceding lesson is what makes a sequence feel like a sequence rather than a list of days.

The worked example is built one step at a time and nothing is erased. A finished example on the board is not a visual instruction plan — Fred Jones warns specifically against the habit we all grew up watching, of making summary graphics at the end. Each step gets its own picture, drawn as that step is taught, so the child sees the ORDER the steps happened in. That order is the method.

The same numbered steps are printed on the student sheet, which is the part that matters most and the part most often left out. Jones: the VIP is first and foremost for the student — a permanent record they can refer to at will. When it is in front of them, helping a stuck child costs about five seconds and one pointed finger instead of a re-explanation, which is what keeps you free to work the room.

After the I DO come two guided examples of the same type, and only then the book. Dimensions gives few problems per lesson because it expects the method to have been built first; three authored examples mean a child has met this type four times before they are alone with it. The book's own problems are clipped onto the slide rather than retyped, so the numbers on the board are the numbers in the child's book.

The question they should be asking themselves

“Have I compared the tens before I looked at the ones?”
Watch for
28 vs 71 is built as a trap: 8 is the biggest digit on the page and it is in the smaller number. A child who answers 28 has compared the ones first, which is the exact error this lesson exists to prevent.

Closure

Which is greater, 34 or 43?