A 12-year old Nigerian boy has made a new discovery in the field of mathematics. The boy, Chika Ofili, has found a new formula to test for the divisibility of 7.
According to Mary Ellis, Ofili's teacher and the Mathematics head at Westminster Under School where Ofili attends, Ofili discovered the formula while doing his holiday homework contained in a book called First Steps for Problem Solvers. The book has several divisibility tests. These can be used to quickly determine whether an integer is divisible by a given number without leaving any remainders. For example, to determine if a number is divisible by 10, check if the last digit is 0. However, the book had no divisibility test for 7.
Not to be deterred, Ofili came up with a formula and backed it up with algebraic proof. In his formula, you take the last digit of any whole number, multiply it by 5 and then add it to the remaining part of the number to get a new number. If this new number is divisible by 7, then the original number is divisible by 7.
For his discovery, Ofili was awarded the Special Recognition Award at the TruLittle Hero Awards.
Other divisibility tests for 7 include taking the last digit off the number, doubling it and subtracting the doubled number from the remaining number. If the result is evenly divisible by 7 (e.g. 14, 7, 0, -7, etc.), then the number is divisible by seven.
Ofili is based in the UK where he lives with his family.