# Interesting Question of the Day – 24 November 2017

How many times in a day do the hour hand and minute hand on a clock make a right angle?

The first new player to comment on the website with the correct answer wins a free drink at their next iQ Trivia show.

I imagine it is twice an hour, so 48 times.

Close. The minute hand makes 24 circuits, and it would be perpendicular to the hour hand twice per hour making 48.

Except that the hour hand also moves.

Want to recalculate?

Hmm.

So if the hour hand goes at 1/12 speed of the minute hand, it’s speed should mean that its slow pursuit eliminates some opportunities for the minute hand to get in a 90 degree position in the 24 hour period.

At 1/12 speed let’s say it eliminates 1/12 of the opportunities. That would be 4 of my 48.

Leaving a final answer of 44.

How’s that?

That’s some good mathematical thinking.

It’s twice every hour, except for 2:00 and 8:00 when there is just one per hour.