Where on the Number Line? Forty to Sixty

Forty to sixty, and nothing outside it. Three number lines fill this 2nd grade number-lines page, each one printed with 40, 45, 50, 55 and 60 and a tick mark standing at every whole number between them. Two orange arrows point down at unlabelled ticks on every line, each with an empty dashed box floating above it, so there are six numbers to name in all. The zero a child would normally count from is nowhere on the sheet, and the smallest number printed anywhere is forty.

Crossing fifty is the reason this range exists. Children who count on confidently inside the forties will sometimes produce forty-ten instead of fifty, and the same hesitation returns whenever a decade boundary sits between the landmark and the arrow. Here the crossing happens on two of the three lines, and it happens in both directions, since 53 is quicker to reach by counting back from 55 than by counting on from 50. That choice of route is what separates a second grader from a first grader on this task, and it is visible in how long the pencil hovers. The narrow range also means every answer is a two-digit number that has to be written correctly.

Print the PDF free and ask which printed number was used before each answer is written; the sentence I started at fifty-five and went back two is the thinking made audible. Number line 20 to 40 is the first grade version of the same idea, number line 60 to 100 carries it up into the nineties, and number line to 50 keeps zero on the page for a child who is not ready to give it up.