Where calculators don't help

How much longer would it have taken for the flight to take off if one of the younger flight attendants had taken charge?

Another resurrected post:

Everyday arithmetic: where calculators don't help

What with the proliferating meme that calculators can substitute for most real-world human calculations, and with restaurant bills that increasingly calculate the various tip possibilities for you (15%, 20%, 25%), it's harder and harder to find examples of cases in which, say, there's no good substitute for knowing your multiplication tables.

But on a recent airplane flight, one such case suddenly jumped out at me. Before the flight took off, the flight attendants were asked to verify that all the passengers were on board. There were six seats per row on what seemed to be a maxed-out flight, and one of the older flight attendants knew exactly what to do. Walking down the aisle, she rapidly counted by 6's: 6, 12, 18, 24, etc...

Think about it... There's no faster way to count rows of airplane passengers than to apply your memorized multiplication tables.

How much longer would it have taken for the flight to take off, I couldn't help wondering, if one of the younger flight attendants had taken charge?