Compare two numbers

What it looks like when your child can do it

• — Shown a jar of 52 marbles and a jar of 34, your child says 52 is more, and 18 more, without counting up from zero on their fingers.
• — Your child looks at the tens before the ones when deciding which of two numbers is bigger.
• — Asked whether 8 seconds or 13 seconds is faster, your child picks 8 and can say why the smaller number wins that one.

How to teach it at the kitchen table

1. 01

   Start with two rows you can see

   Line up 7 spoons in one row and 4 spoons in a row right under it. Your child can see which row runs longer. The spoons left over at the end are the difference, 3.

2. 02

   Compare the biggest place first

   For two-digit numbers, look at the tens before the ones. In 52 and 34, five tens beats three tens, so 52 is bigger no matter what the ones say.

3. 03

   Find how much more

   Take the smaller number away from the bigger one. 52 minus 34 is 18. Counting up works too: 6 gets you from 34 to 40, and 12 more gets you to 52.

4. 04

   Say it in a whole sentence

   Ask your child to say both numbers, which is bigger, and by how much, with the unit. "The red jar held 52 marbles, 18 more than the blue jar."

5. 05

   Read the question before picking a winner

   "Which holds more" wants the bigger number. "Which is faster" wants the smaller number of seconds. Ask your child to read the question out loud before deciding.

You will need: Spoons, buttons or any small things to line up · Paper and a pencil · A tape measure

Try it together

1. Try 1

   Write 34 and 52. Ask which is bigger and how much bigger.

   Listen for  52, by 18. Listen for the tens being compared first, then 52 minus 34, or counting up from 34 to 40 and on to 52.

2. Try 2

   Write 58 and 85. Ask which is bigger.

   Listen for  85. Same two digits in different places. If your child hesitates, ask how many tens each one has, 5 or 8.

3. Try 3

   Say: a toy car took 11 seconds to roll down the hall and a ball took 7 seconds. Which was faster, and by how much?

   Listen for  The ball, by 4 seconds. The smaller time is the faster one, so here the smaller number wins.

4. Try 4

   Say: one sunflower is 93 centimeters tall and the other is 78 centimeters. How much taller is the first one?

   Listen for  15 centimeters, because 93 minus 78 is 15. Counting up works too: 2 to reach 80, then 13 more to 93. Listen for the unit on the end of the answer.

Watch for

• — Comparing the ones first, so 29 looks bigger than 41 because 9 is bigger than 1.
• — Treating the bigger number as the winner every time, even when the question asks which was faster.

If it is not there yet

• — Go back to two rows of real objects lined up one under the other, and count only the extras at the end of the longer row.
• — Use a tape measure as a number line. Find both numbers on it and count the steps from one to the other.

A few days of this is normal, and it is time well spent. The lesson will still be there, and it will go faster.

Where this skill comes up

• How Scientists Actually Find Out · Lesson 23

  What the Numbers Say

  Needs it because the conclusion turns on which recorded value is larger and by how much.