Odd and Even Numbers Under 100: Look at the Ones Box

Twelve two-digit numbers are laid out on this 2nd grade page in two columns of six. Each is written as two separate boxes under the headings T and O, with the ones box tinted coral, and beside it sit two circles under the words odd and even. A rule is printed in a band across the top: even numbers end in 0, 2, 4, 6 or 8, and odd numbers end in 1, 3, 5, 7 or 9. The sheet shown runs 86, 37, 21, 32, 58, 99, 65, 55, 42, 14, 53 and 70.

Splitting the number into two boxes is what teaches the rule rather than merely stating it. A child who has only met odd and even below twenty has to be shown that the tens digit is irrelevant, and printing 86 as an 8 and a tinted 6 makes the irrelevance visible before the rule is applied. Six of the twelve are even and six odd, and the pairs 55 and 65, 42 and 14 keep the same digits in different places.

One sheet, twelve numbers, twelve ticks. It is the fastest page in the family once the rule lands, which makes it a good check rather than a lesson. The headings T and O are not explained on the sheet, so say tens and ones as you hand it out. Use it after the dot and sharing faces, so the rule arrives as a shortcut for something already understood.