Compare and order numbers to 100

What you will learn

• Compare and order numbers to 100

Models used: number sentences, stories, tables.

Before you start

• Read and write number names to 100

Look at the biggest groups first

Compare 32 and 28. Each long row represents a group of ten.

1. The number at the top of each column is the value of one counter in that column.

   Compare 32 and 28. Each long row represents a group of ten.

   One extra large unit can outweigh several smaller units. Equal large places make us look at the next place.

2. The number at the top of each column is the value of one counter in that column.

   32 has three tens. 28 has only two tens. Those tens decide the comparison.

   A digit tells us how many units there are. Its position tells us what size those units are; that is why a zero can matter.

3. Both bars use the same scale. Compare their lengths and read the names beside them.

   Even though 8 is more than 2, 28 is less than 32. Compare the tens before the ones.

   28 < 32

   3232

   2828

   Difference: 4

Worked example: A new example, together

Put 94, 32, 91 in increasing order.

1. Compare place values. Read each value with the heading above its column.

   Line up the place-value columns. Find the first difference from the left.

   Increasing order lists each value from smallest to greatest.

   Compare place values

   Numbers
   94
   32
   91

2. Compare place values. Read each value with the heading above its column.

   Compare the greatest place first.

   Compare place values

   Numbers
   94
   32
   91

   Put 94, 32, 91 in increasing order.

   32, 91, 94

3. Compare place values. Read each value with the heading above its column.

   Compare the greatest place first.

   Compare place values

   Numbers
   94
   32
   91

4. Compare place values. Read each value with the heading above its column.

   Continue through smaller places when digits match.

   Compare place values

   Numbers
   94
   32
   91

5. Compare place values. Read each value with the heading above its column.

   Smallest to greatest: 32, 91, 94.

   Compare place values

   Numbers
   94
   32
   91

6. Compare place values. Read each value with the heading above its column.

   Check the result against the question we started with.

   Each next number is at least as large as the previous number.

   We found 32, 91, 94. Increasing order lists each value from smallest to greatest.

   Compare place values

   Numbers
   94
   32
   91

Common mistakes to discuss

• Longer looks larger. Compare the greatest place first, not the number of digits on the page. 0 thousands beats nothing: 998 is less than 1002 because the thousands differ.

Check your understanding

• Compare and order numbers to 100
• justify a comparison with place value
• check the answer against the original quantities and units

Explain your reasoning to an adult, then try a fresh question in the interactive lesson. A result from one attempt is not proof of lasting mastery.