Count Up to the Target

How far from 48 to 62? Jump to the ten, then jump in tens.

Game Adjusts as you go Add and subtract within 100 2.OA.B.22.NBT.B.52.MD.B.6 ALPACA · Early operations ARF · Subtraction facts

Counting on in ones? Start here. A short lesson on a number line, where one marker jumps ten at a time so you can see that every jump of ten is the same size. About about 4 minutes.

Show me jumps of ten → How do jumps of ten work again?

▤ Print this All of 2nd grade

For grown-ups

How long: 5 to 10 minutes is plenty. Short and frequent beats long and occasional — the early-numeracy trials with the largest effects ran eight weeks or less.
The strategy to reinforce: “Jump to the ten” — From 48, jump 2 to get to 50. Then jump 10s. Add the jumps: that is the answer. If they stall, remind them of this rather than giving the answer.
When they get one wrong: the page shows the working. Read it together rather than moving straight on. Feedback that explains is worth several times more than feedback that only marks right or wrong, and that gap is wider in maths than in any other subject.
It adjusts as you go: this one gets harder while they are getting them right and easier if they are not, aiming to keep them succeeding about four times in five — hard enough to be worth doing, not hard enough to stop being fun. The score is how deep they got rather than how many they answered, because the difficulty moved. Nothing is stored — it starts fresh every time the page loads.
On the timer: it is off unless you turn it on, and it is never needed. Use it only once the skill is comfortable, never to introduce it.
Print it too: doing the same problems on paper a few days later is worth more than doing twice as many today.

What this practises

Finding a difference by counting up from the smaller number in friendly jumps.

Counting up is the strategy children invent before they are taught anything, and IM grade 2 puts it on the number line before the vertical algorithm arrives — a difference is a distance, and 62 − 48 is a short distance however big the digits look. Number Talks treats naming the jumps out loud as the whole exercise, because the strategy is only useful if the child can choose it. The jump picture is drawn for the first third of the rounds and then withdrawn: concreteness fading beats keeping the support (Fyfe 2014), and a child who can only do this with the diagram has not learned it.

The underlying idea: A difference is a distance. Counting up measures it, and does not need the standard algorithm at all.
Where this sits in Illustrative Mathematics: 2nd grade Unit 2: Adding and Subtracting within 100 · 2nd grade Unit 4: Addition and Subtraction on the Number Line
Sources: Illustrative Mathematics / Kendall Hunt (2024) · Institute of Education Sciences / What Works Clearinghouse (2021) · Parrish (2010) · Fyfe et al. (2014) all references →

Related measured skills: ALPACA · Early operations, ARF · Subtraction facts. What this means