L1 · Familiar sequences: even and odd numbers; position in ordinal numbers

Learning goal

“I can tell whether a number is even or odd by pairing it up and by looking at its last digit, and I can name the position of a term in a sequence with ordinal numbers like 1st, 2nd, 3rd and 4th.”

Sequence — a list of numbers written in a certain order. Each number in the list follows the one before it.

Term — one number in a sequence. In 3, 6, 9, the number 6 is a term.

Even number — a number whose counters pair up with none left over. Even numbers end in 0, 2, 4, 6 or 8.

Odd number — a number whose counters pair up with one left over. Odd numbers end in 1, 3, 5, 7 or 9.

Worked example

Is 14 even or odd? Is 15? Step 1: Pair the counters. 14 counters make 7 pairs with none left over, so 14 is even. Step 2: 15 counters make 7 pairs with 1 left over, so 15 is odd. Step 3: Check the last digits. 14 ends in 4 - an even digit. 15 ends in 5 - an odd digit. The last digit always gives the same answer as pairing. Number-line picture: the even numbers are every second landing when you count by 2s from 0: 0, 2, 4, 6, 8, 10 ... The odd numbers are the landings in between. Say it plainly: only the LAST digit decides even or odd. The other digits do not matter.

Check yourself — explain it

Why is 23 odd?

Paired problem — example still visible

Is 38 even or odd? Say how you know. -> Even - it ends in 8, and its counters make 19 pairs with none left over

Faded completion — last step is yours

"A number ends in 7. Its counters pair up with ___ left over, so the number is ___." -> 1; odd

Ready to practise?

10 scored questions with a 3-rung hint ladder. Mastery needs 8/10 plus both gate questions.

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