21 x 2☐ = 50☐ 705 x 1☐ = 9☐65 5☐7 x ☐49 = 85☐73 ☐7 x 4☐3 = 12☐71 ☐35 x 2☐2 = 77☐20 1☐47 x ☐81 = 59☐807

Each red box represents a missing digit.
Can you find out what they are?

## A Mathematics Lesson Starter Of The Day

Topics: Starter | Arithmetic | Problem Solving

• Miriam Candelaria, Toa Baja, Puerto Rico
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• It is fun and a great day starter. I would really appreciate the answer key, though.
• Transum,
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• Thanks Miriam, you'll find the answers to most starters right at the bottom of the page for those who have a Transum subscription.
• Helsby High School, 10y4
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• Most of the class thought this was a good starter. Thank You
• Mrs O'hagan's 3rd Yr Class, Holyrood Sec School Glasgow
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• We enjoyed the activity and would like similar but even more challenging!
• 6LC, West Kidlington Primary School
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• It was quite hard but we really enjoyed it!
• Transum,
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• What strategies might you use to do this activity? Most people would probably reach for their calculator straight away but the task requires a more thoughtful approach. Each calculation has a different form and different suppositions can be made depending on the digits that are given. Trial and improvement with a planned range of possible missing digits and a calculator used wisely will help solve this puzzle. Each time the page is refreshed a different set of calculations will appear giving plenty of opportunity for practice.
• Maths Brainy Badgers, United Kingdom
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• We found it fun and challenging in a good way.

How did you use this starter? Can you suggest how teachers could present or develop this resource? Do you have any comments? It is always useful to receive feedback and helps make this free resource even more useful for Maths teachers anywhere in the world.

Previous Day | This starter is for 1 December | Next Day

 21 x 24 = 504 705 x 13 = 9165 577 x 149 = 85973 27 x 473 = 12771 335 x 232 = 77720 1247 x 481 = 599807

Note to teacher: Doing this activity once with a class helps students develop strategies. It is only when they do this activity a second time that they will have the opportunity to practise those strategies. That is when the learning is consolidated. Click the button above to regenerate another version of this starter from random numbers.

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The 1st December is the date to start opening the doors of the 2024 Mathematics Advent Calendar.

For Students:

For All: