On Saturday, November 9, 2019, a 12-year old Nigerian boy based in the United Kingdom, Chika Ofili, made history after scooping an award at the Trulittle Hero Awards 2019.
The Trulittle Hero Award, which annually rewards kids and young people all over the UK for achieving remarkable feats under the age of 17, recognised the outstanding discovery of the Nigerian who uncovered a new mathematical formula used to test for divisibility by seven.
Read more about another Nigerian discovery
Something very exciting happened last Friday when one of my pupils, Chika Ofili, popped into the classroom and asked if he could tell me something he had thought of over the summer holidays. I was intrigued…
Mary Ellis
Chika’s math teacher and head of mathematics department at the Westminster Under School (an independent preparatory school for boys aged 7 to 13), Mary Ellis, noted the genius made the discovery while simply solving an holiday assignment. Ellis had given Chika a book which contained a lot of divisibility tests used to examine the possibility of dividing a figure with the use of numbers 2 to 9, but the book did not contain any memorable test for checking divisibility by 7.
In his bid to solve his math assignment, Chika devised a new formula which involves taking the last digit of any whole number, multiplying it by 5, before doing an addition with the remaining part of the number to get a new number. Chika knew he needed algebraic proof to back his discovery, which he did by figuring out that the new number if divisible by 7 means the original number is also divisible by 7.
See sample of Chika’s discovery below:
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 are 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 are 31 nor our original number, 114.
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Sources:
Lifestyle.thecable NG
Dailytrust NG
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