31 coins are tossed.

The probability that heads comes on $n$ of them, where $1 \equiv n \mod 3$ , is

$\dfrac{1}{2}$
$\dfrac{1}{4}$
None of these
$\dfrac{1}{3}$

**
This section requires Javascript.
**

You are seeing this because something didn't load right. We suggest you, (a) try
refreshing the page, (b) enabling javascript if it is disabled on your browser and,
finally, (c)
loading the
non-javascript version of this page
. We're sorry about the hassle.

Incidentally the difference between the correct answer and $\dfrac{1}{3}$ approximately $1.55 \times 10^{-10}$