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Dinosaur Egg Code Breaker: Free Printable Worksheet for Year 1

  • ForYear 1
  • StageKey Stage 1
  • CostFree
  • FormatPrintable PDF
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Dinosaur Egg Code Breaker is a free printable maths worksheet for Year 1 (ages 5 to 6), in Key Stage 1. Each dinosaur egg has an addition with a missing number. Children work out the number, find it in the code and write the matching letter. The letters spell a name. It is a screen free way to practise number bonds to ten.

It comes from the Mini Minds Hub, the free library of printables from Jaques of London, the British games and toy company that has been making games for families since 1795. Print both pages. Give page 1 to your child and keep page 2 for yourself. Black and white printing works well.

What is on the sheet

Children see a code that links missing numbers to letters. Below it, each dinosaur egg shows an addition that makes ten, with one number hidden. Children work out the hidden number, look it up in the code and write the letter on the line. There is space to answer each question. When every egg is done, the letters spell a name, which tells children they have cracked the code.

  • Missing number
  • 2
  • 3
  • 4
  • 6
  • 7
  • Egg 1: 7 + ? = 10 Letter:
  • Egg 2: 3 + ? = 10 Letter:
  • Egg 3: 6 + ? = 10 Letter:
  • Egg 4: 4 + ? = 10 Letter:
  • Egg 5: 8 + ? = 10 Letter:

A different example

9 + ? = 10

This example is different from the sheet. It shows two ways to find a missing number.

Method 1: count on
  1. Say the first number, 9, and keep it in your head.
  2. Count on to 10 and hold up one finger for each count.
  3. Only one finger is up, so the missing number is 1.
Method 2: use a ten frame
  1. Put 9 counters on a ten frame.
  2. Count the empty spaces left in the frame.
  3. There is 1 empty space, so the missing number is 1.
9 + 1 = 10, so the missing number is 1

Ways to build number bonds to ten

Use ten fingers

Hold up all ten fingers. Fold some down and ask how many are still standing. The folded and standing fingers always make ten. Try it with different numbers.

Fill a ten frame

Put some counters on a ten frame. Ask your child to count the empty spaces without counting the counters again. The counters and the spaces together make ten.

Quick partners

Say a number from 1 to 9 and ask for the partner that makes ten. Start slowly, then speed up. Swap roles so your child can test you.

Write it both ways

Show that 9 + 1 = 10 and 1 + 9 = 10 mean the same thing. Try it with 5 + 5 too. This helps children see that order does not change the total.

Why use a code breaker for number bonds?

Number bonds to ten are pairs of numbers that add up to ten. Children who know them quickly find bigger sums easier later, such as adding by making a ten. Knowing them by heart takes lots of short, varied practice. Finding a missing number is a useful version of that practice, because children must think about the whole and one part, not just add two numbers.

A code gives children a reason to get each answer right. If the number is wrong, the letter will be wrong and the name will not make sense. Children can spot this themselves and go back to check. Dinosaur eggs add a playful theme that many Year 1 children already love, so the practice feels like a puzzle.

Dinosaur egg facts

  • Dinosaurs laid eggs, just as many reptiles and birds do today.
  • Some dinosaur eggs have turned into fossils, which is how we know about them.
  • People who study fossils are called palaeontologists.
  • Dinosaur eggs were not all the same size or shape.
  • Birds living today are close relatives of dinosaurs.

Skills and curriculum link

  • Number bonds to ten
  • Finding a missing number
  • Following a code
  • Careful reading
  • Writing letters

Ideas to help your child

  • Think of ten as a wholeTen is the whole. One number is a part. The missing number is the other part. Say it this way when your child is stuck.
  • Count on, do not start againChildren can say the number they have, then count on to ten. Use fingers, counters or a number track to keep track of the steps.
  • Say it aloudReading the sentence aloud helps. For example, say the first number, then "and how many more make ten?"
  • Check with a drawingIf an answer feels uncertain, draw ten small circles. Shade some, then count the rest to see if the total is ten.

Key words

  • Number bondTwo numbers that add together to make a total. A bond to ten makes ten.
  • Missing numberA number that is hidden in a sum. You find it to make the sum true.
  • CodeA set of rules that lets you swap one thing for another, such as a number for a letter.
  • TotalThe amount you have when you put two parts together.
  • Ten frameA grid with two rows of five boxes. It helps children see a number as part of ten.
  • Count onStart at one number and say the next numbers in order to reach another.

How to use it

  1. Print both pages. Page 1 is for your child. Keep page 2, which has the notes, help ideas and answers.
  2. Read the first egg together. Talk about what the question mark is hiding.
  3. Let your child work out the missing number, find it in the code and write the letter on the line.
  4. Check with the answers on page 2. Ask, "How did you find that number?" The thinking matters as much as the letter.
  5. Come back to it another day. Repeating a familiar activity builds confidence.

Help, stretch and game ideas

If it feels too hard

Give your child counters or a ten frame. Put the first number of counters on the frame, then count the empty spaces together. Say the numbers aloud as you count. Do the first egg together, then let your child try the next one alone.

To stretch confident children

Ask your child to write a new egg for a friend to solve, using a different bond to ten. Then try hiding the first number instead, such as ? + 1 = 10. Can they work out how the question changes?

Make it a game

Count ten small objects together. While your child closes their eyes, hide some under a cup. When they open their eyes, they count the objects they can see and say how many are hiding. Lift the cup to check.

Mistakes to watch for

Watch forA child writes 10 in the gap because it is the total on the page.

Try thisPoint to the question mark. Ask, "What do I add to this number to reach ten?" Use counters to show it.

Watch forA child counts the number they start with as the first step, so the answer is one too big.

Try thisSay the start number first, then count on. Only the new numbers get a finger.

Watch forA child finds the right number but writes the letter from the wrong place in the code.

Try thisRun a finger along the code to the number, say it aloud, then write the letter beside it.

Watch forThe letters do not spell a name at the end.

Try thisCheck each egg again, one at a time. A single wrong number changes a letter. Use counters to prove each answer.

Talk about it

  • What does the question mark mean in this sum?
  • How did you work out the missing number? Is there another way?
  • How do you know the number you found is right?
  • What would happen to the code if we had the wrong number?
  • Which number bonds to ten do you already know without counting?
  • If you laid a dinosaur egg, what would you name your baby dinosaur?

Take it off the page

Dinosaur egg hunt

Hide ten paper eggs around a room. Tell your child how many you hid, let them find some, then ask how many are still hiding.

Salt dough or play dough eggs

Make ten small eggs from play dough. Put them in two nests and say how many are in each. Count to check they still make ten.

Ten in the box

Put ten pasta shapes in an egg box with spaces for twelve. Take a few out and ask how many are left to make ten again.

Who it is for

Parents

Sit beside your child for the first egg, then let them lead. Keep it relaxed and stop when they have had enough. If they get stuck, offer counters or a ten frame and ask them to count the empty spaces.

Teachers

Use it as a starter, plenary, early finisher task, homework or table activity. It needs no preparation beyond printing. It fits teaching on number bonds, and page 2 gives support and stretch ideas for mixed ability groups.

Home educators

Pair the sheet with books about dinosaurs, outdoor egg hunts or play with counters. The sheet is free to print again for brothers, sisters or revision a few weeks later.

Where this fits in learning

Before this, children count to ten and beyond, and learn that a number can be split into two parts. They use objects, fingers and ten frames to see that the parts always make the same whole. Knowing this makes missing number questions much easier.

After this, children use bonds to ten to learn bonds within 20 and to add by making a ten. In Year 2 they recall addition and subtraction facts to 20 and use them to work out related facts with larger numbers. Quick recall of bonds to ten is the base for all of this.

Questions parents and teachers ask

What age is Dinosaur Egg Code Breaker for?

It is written for Year 1 (ages 5 to 6), in Key Stage 1. Older children who need more practice with number bonds can use it too, and younger children may enjoy it with an adult.

What will children practise?

Children practise number bonds to ten and finding a missing number. They also follow a code to turn each number into a letter, which gives a reason to check their answers.

How long does it take?

It depends on the child. Let them work at their own pace and take a break if they tire. You can do a few eggs at a time and come back to the rest another day.

What if it feels too hard?

Give counters or a ten frame so your child can count on to ten. Do the first egg together, say each step aloud, and let them try the next one by themselves.

Do I need to print in colour?

No. It prints well in black and white on plain A4 paper. Print both pages, give page 1 to your child and keep page 2 for yourself.

Is it suitable for teachers to use in class?

Yes. Teachers can use it as a starter, plenary, early finisher task, homework or table activity. It needs no preparation beyond printing, and page 2 has help and stretch ideas.

Can I use it for home education?

Yes. Home educators and tutors can use it on its own or as part of a wider maths plan. It is free to print again for brothers, sisters or revision later on.

Preview the full PDF

Made by Jaques of London, making games for families since 1795. A printable supports classroom learning and does not replace a teacher.

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