Comparing to 100 — for parents

Comparing to 100 — for parents

Comparing to 100 — for parents

Coming out of 1st grade, your child can compare numbers up to 20. In 2nd grade the skill stretches to numbers up to 100 — but this isn't just a quantitative step. It requires a solid grasp of place value (tens and ones) and the ability to make a two-step decision rather than a one-glance one.

Why this matters

Comparing within 100 is more than just another chapter. It's a bridge:

  • From 1st grade ("which number is bigger?") into 3rd grade ("which number up to 1000 is bigger?").
  • Toward column addition and subtraction, where the child needs to separate tens from ones automatically.
  • Toward estimation and rounding, which arrive in 3rd and 4th grade.

If a 2nd-grader struggles with comparing, the trouble carries forward. That's why it's worth investing time now.

Common mistakes and how to spot them

1. Comparing the digits, not the place values.

Your child says 18 > 81 because they look at the digits 1 and 8 and notice that 8 > 1. They don't account for the fact that the 8 in 81 stands for 80 (eight tens) while the 8 in 18 is just 8 (eight ones).

Fix: hands-on materials — building blocks, coins worth ten and one. Have the child physically build "1 ten and 8 ones" against "8 tens and 1 one" and feel the difference in their hands. 2. Writing the < and > sign the wrong way round.

The child writes 45 < 38 (which makes no sense) instead of 45 > 38.

Fix: the "crocodile mouth" — the crocodile always wants to eat the bigger number, so the open mouth always faces the bigger one. After a few repetitions it sticks. 3. Guessing when the tens are equal.

With 63 vs 68 the child hesitates — they see two equal sixes and lose their footing.

Fix: the two-step method from the skill article ("tens first, then ones"). Practise on pairs with matching tens: 41/47, 32/37, 85/89.

Activities for home practice

Short, regular practice works better than one long session a week.

  • Number cards. Cut out cards with numbers 10–99. Flip two over; the child says which is bigger and which sign goes between them.
  • Coins and tens. Put out two piles of coins (worth 10 and 1). The child first counts how many cents are in each, then compares.
  • "Bigger wins" game. Card with a number face up; whoever has the bigger one takes both cards. Simplest, most effective game there is.
  • Real-world prompts. At lunch: "I have 24 lentils, you have 31. Who has more?" On a walk: "That sign says 50 km/h, the next one says 60 km/h. Where can you drive faster?"

When to seek extra help

Most children get this within a few weeks of 2nd grade. But it's worth talking to the teacher or a specialist if:

  • After several months of practice, the child still can't tell tens from ones using concrete objects (cubes, coins).
  • They flip the < / > sign 9 times out of 10, even after repeated mnemonic practice.
  • They avoid tasks with numbers above 20 and say "this is hard," even when the task is straightforward within 100.

These can be early signs of a deeper number-sense problem or dyscalculia. Catching it early makes a big difference.

Summary for the parent

  • Comparing within 100 is a bridge, not a stand-alone exercise. Time spent here pays off in later topics.
  • The most common mistake is comparing the digits rather than the place values — the fix is hands-on material.
  • Short, regular practice (5–10 minutes daily) beats long sessions.
  • If difficulties persist, talk to the teacher sooner rather than later.