JAMB 1998 · UME · Q50

If $x$ and $y$ can take values from the set $\{1, 2, 3, 4\}$ , find the probability that the product of $x$ and $y$ is not greater than 6.

Worked solution (try it first)

$x$ and $y$ each have 4 values, so there are $4 \times 4 = 16$ ordered pairs.
Products not greater than 6: $x = 1$ with any $y$ (4 pairs), $x = 2$ with $y = 1, 2, 3$ (3 pairs), $x = 3$ with $y = 1, 2$ (2 pairs) and $(4, 1)$ .
That is 10 pairs.
So the probability is $\frac{10}{16} = \frac58$ , option A.