What comes next?

Number Theory Level pending

Suppose there is an operation $\oplus$ such that

$1 \oplus 2 \oplus 3 = 9$ $2 \oplus 3 \oplus 4 = 2$ $3 \oplus 4 \oplus 5 = 8$ $4 \oplus 5 \oplus 6 = 9.$

What is the value of $5 \oplus 6 \oplus 7 = ?$

5 3 4 2

1 solution

Ossama Ismail
Feb 8, 2016

Answer is 5

$a \oplus b \oplus c$ = keep adding the sum of the digits in $a \times c$ and $b \times c$ till it reduces to a single digit number.

$5 \oplus 6 \oplus 7 = 5 \times 7 , 6 \times 7 = 35 , 42 = 8,6 =14=5$