JAMB 1997 · UME · Q21

Binary operations

Two binary operations $*$ and $\oplus$ are defined by $m * n = mn - n - 1$ and $m \oplus n = mn + n - 2$ for all real numbers $m$ , $n$ . Find the value of $3 \oplus (4 * 5)$ .

Worked solution (try it first)

Work out the bracket with the $*$ rule: $4 * 5 = 4 \times 5 - 5 - 1 = 14$ .
Now use the $\oplus$ rule with $m = 3$ and $n = 14$ : $3 \oplus 14 = 3 \times 14 + 14 - 2$ .
That is $42 + 14 - 2 = 54$ , option C.

Report a problem with this question