### Everyday Heroes

# Everyday Heroes- Chika Ofili

Chika Ofili is a 12-year-old Nigerian awarded for making mathematics easy to learn. He was awarded at the TruLittle Hero for discovering a new way to divide in mathematics. The UK-based 12-year-old has made both Nigeria and Africa proud.

**Chika: On the Road to Greatness**

Chika’s mathematics teacher, Miss Mary Ellis who is also the head of the maths department at Westminster under School gave Chika a book called First Steps for Problem Solvers (published by the UKMT) to study during the holidays. That book was instrumental to Chika’s discovery. The book contained several divisibility tests, which are used to quickly work out whether a number is exactly divisible by either 2, 3, 4, 5, 6, 7, 8 or 9 before you start dividing. Chika, however, noted that there was no test listed for checking divisibility by 7. This was not listed because there is no easy or memorable test for dividing by 7. This was Chika’s self-imposed task; to solve this problem.

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**Chika’s test**

Chika discovered that if you take the last digit of any whole number, multiply it by 5 and then add this to the remaining part of the number, you will get a new number. If this new number is divisible by 7, then the original number is divisible by 7. Chika then demonstrated his new formula in front of the school faculty. Afterwards, Miss Ellis got a neutral mathematics guru to test the theory. This person was Simon Ellis her younger brother who also taught mathematics.

He tested the theory and wrote an algebraic proof for it. He further discovered that the test works if you start by multiplying the last digit by 12, 19, 26, 33…and then add it to the remaining part of the number.

For example, take the number 532

53 + 2 x 5 = 63

63 is a multiple of 7,

So 532 is a multiple of 7 (and therefore divisible by 7)

Or take the number 987

98 + 7 x 5 = 133

13 + 3 x 5 = 28

28 is a multiple of 7,

So both 133 and 987 are multiples of 7

In fact, if you actually keep going, you will always end up with either 7 or 49, if the original number is divisible by 7.

For example, take the number 2996

299 + 6 x 5 = 329

32 + 9 x 5 = 77

7 + 7 x 5 = 42

4 + 2 x 5 = 14

1 + 4 x 5 = 21

2 + 1 x 5 = 7

7 is a multiple of 7 and so is 21, 14, 42, 77, 329 and the original number 2996.

The opposite is also true in that if you don’t end up with a multiple of 7, then the original number is not divisible by 7.

For example, take the number 114

11 + 4 x 5 = 31

3 + 1 x 5 = 8 and since 8 is clearly not divisible by 7, neither is 31 nor our original number 114.

But mathematically, we needed to find proof. Once a theorem is proved mathematically, it will always be true.

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Pythagoras proved his famous theorem over 2,500 years and when he died, he knew it would never be disproved. It is important to realise that a result cannot be proved by finding thousands or even millions of results which support it.

“I woke up early on Saturday morning still thinking about Chika’s test and rang my younger brother, Simon Ellis, who also happens to teach Maths, and asked him if he had ever come across the test. He hadn’t and immediately set about trying to write a proof. An hour later he sent me a watertight algebraic proof! He also discovered that the test works if you start by multiplying the last digit by 12, 19, 26, 33 … and then add it to the remaining part of the number. And furthermore, it works if you double the last digit and then subtract it from the remaining part of the number, or if you multiply the last digit by 9, 16, 23, 30 … and subtract. And actually the doubling and subtracting test can be easily found on the internet. But we both agreed multiplying the last digit by 5 and adding it to the remaining part of the number is much more appealing!-Miss Ellis

He won an award at the TruLittle Hero award over the weekend for discovering a new way to divide in mathematics. The young mathematician genius’ new formula created new divisibility by seven in mathematics. It should be noted that the TruLittle Hero Awards is a yearly event which gives recognition and celebrates marvelling achievements of children and young people who are still under the age of 17 years in the UK.

**Sources:**

Legit

Dailytrust

* Featured image source: @westminsterUS -Twitter*

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