# Package 1-3: Let’s get magical!

In this activity your child will use magic tricks to develop mathematical reasoning and practise their skills in mental computation.

Week 2 - Package 3 - Year 5 and 6 Mathematics - Let’s get magical!

Things you need

Ideal Back up

Pencils or markers

Paper

Numbered cards 0-9

UNO cards

# Why is this activity important?

Magic tricks provide great opportunities for students to develop mathematical reasoning and practise their skills in mental computation. This trick is helpful for practising addition and subtraction facts. It also helps students develop skills in choosing efficient strategies for solving addition and subtraction problems. Practising the magic trick multiple times helps students develop confidence, consolidate skills in mental computation and helps them see the maths underlying the magic.

# Before you start

You need some pens and a piece of paper.

Numbered cards are required for the optional activities.

# What your child needs to know and do

Student needs to be able to add and subtract 3-digit numbers.

Watch the video Let's get magical!

# What to do next

• Choose a 3-digit number where each digit is smaller than the previous one (but they don’t have to be in order. For example, 982 or 531.)

• Then, reverse the digits and subtract the second number from the first one. So, if I had chosen 531, I would now work out 531 – 135. The answer is 396. (If you get 99, record your answer as 099.)

• Next, reverse your new number. For example, from 396 I can make 639.

• Finally, add these last two numbers together. For example, 396 + 639.

• Here comes the magic...

Activity too hard? Activity too easy?

Complete a different magic trick (‘Predict your puzzle’), detailed below

Try using a different strategy to do the calculations for the magic trick. For example, you might like to use a calculator. Then, explore what happens if you follow the same rules but starting with a 2-digit number (for example, 76 or 82).

Complete several times to practice using mental strategies with 2-digit numbers. Then try the trick again with 3 digit-numbers.

Investigate what happens with this magic trick using 4-digit numbers and 5-digit numbers. Complete several times to practice.

Work together to explore which mental computation strategies are the most efficient when adding and subtracting.

You can also work together to investigate how this magic trick works!

• Try another starting number and test it out again...is the final answer still 1089?

• Explore what happens if you use the same process, starting with a 2-digit number or a 4-digit number...

• Why do you think this might be happening?

# Now try this magic trick!

1. Choose a number in the grid and circle it.

2. Choose another number which is not in the same row or column as the first number and circle it.

3. Pick a third number which is not in the same row or column as either of the other numbers you have circled.

4. Pick a fourth number which is in no other column or row as the other circled numbers.

5. Add all 4 numbers which are circled together.

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1. Try this puzzle again.

2. Share it with a family member.

3. Explore....how does this work?

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Example: 3 + 8 + 10 + 13= 34