Skip Counting in 2s, 5s and 10s

What you will learn

• Count forwards and backwards in $2$s, $5$s and $10$s, up to $100$.
• Spot the pattern in the last digit of each list.
• Use skip counting to count groups of the same size.

Before you start: you should be able to count to $100$ in ones and know what tens and ones are. If not, try Counting and Place Value first.

The idea

Counting one by one is slow when there are lots of things. A shelf holds $8$ pairs of socks. Counting every sock from one is a long job. But you can say “two, four, six, eight, ten, twelve, fourteen, sixteen” and you are done, because each pair is two socks.

That is skip counting: counting in equal jumps. You skip the numbers in between and only say the ones you land on. Every jump is the same size, and that size tells you what you are counting in.

Counting in 2s

Start at $0$. Jump $2$ each time. You say "$2, 4, 6, 8, 10, 12, 14, 16, 18, 20$".

Look at the last digit of each number you land on: $2, 4, 6, 8, 0$, then the same five again. Counting in $2$s never lands on a number ending in $1, 3, 5, 7$ or $9$.

Things that come in twos are everywhere: shoes, eyes, wheels on a bike, wings on a bird.

Counting in 5s

Jump $5$ each time: "$5, 10, 15, 20, 25, 30$" and on to $100$. Every number ends in $5$ or $0$, taking turns.

Fingers on one hand make a group of $5$, so five-counting is easy to try: count a hand, then the next hand, and keep adding five.

Counting in 10s

Jump $10$ each time: "$10, 20, 30, 40, 50, 60, 70, 80, 90, 100$". Every number ends in $0$. The tens digit goes up by one each jump, which is the same pattern you met in counting tens in Counting and Place Value.

Counting back

Skip counting works backwards too. Start at a number and take the same jump away each time. Counting back in $10$s from $50$ goes "$50, 40, 30, 20, 10, 0$". Counting back in $5$s from $30$ goes "$30, 25, 20, 15, 10, 5, 0$".

Starting from any number

You do not have to start at $0$. Start at $23$ and count on in $10$s: "$23, 33, 43, 53$". The ones digit stays the same and the tens digit goes up one each time. Start at $7$ and count in $2$s: "$7, 9, 11, 13$". The ones digit still follows its pattern, but now it is $7, 9, 1, 3, 5$ instead.

Counting groups

Skip counting is the quickest way to count equal groups. Pick the jump that matches the group size.

• Shoes in pairs: count in $2$s.
• Fingers on hands: count in $5$s.
• Coins that are all $10$ pence: count in $10$s.

You need to keep track of how many groups you have counted. Use a finger for each group, or say the group number quietly in your head. The last number you say is the total.

Worked examples

Example 1: Counting shoes

Anya lines up $7$ pairs of shoes. How many shoes is that?

1. Each pair is $2$ shoes, so count in $2$s.
2. Say one number for each pair and fold a finger down each time: "$2, 4, 6, 8, 10, 12, 14$".
3. Seven fingers are down, so stop at $14$.

Answer: $14$ shoes.

Example 2: Counting coins

Leo has six $5$ pence coins. How much money does he have?

1. Every coin is worth $5$, so count in $5$s.
2. One number for each coin: "$5, 10, 15, 20, 25, 30$".
3. Six coins counted, so the total is $30$.

Answer: $30$ pence.

Example 3: Finding a missing number

Here is a skip counting pattern with a gap: $20, 30, \_, 50, 60$. Which number is missing?

1. Find the jump. From $20$ to $30$ is $10$, so this is counting in $10$s.
2. Check the jump again with the end: from $50$ to $60$ is $10$. Same jump, so the pattern holds.
3. The missing number is $10$ after $30$, which is $40$.

Answer: $40$.

A common slip is changing the jump half way. In "$5, 10, 15, 20, 30$" the last jump is $10$, not $5$. Check each jump against the first one before you trust your list.

Why it matters

Skip counting is how people count money, tickets, steps and sweets without losing track. It also sets up multiplication. Counting $5$ hands in $5$s is the same as the fact “five fives are twenty-five”, so the lists you learn here turn into the $2$, $5$ and $10$ times tables later on. And the patterns in the last digits help you spot mistakes straight away: a list of $5$s that ends in $7$ must have gone wrong somewhere.