- Five-eighths? Don't you mean three-quarters?
- Why, you're right.

9 seconds sound clip from the Back to the Future Part II movie soundboard.

You can hear this line at 01:13:51.060 in the Blu-ray version of the movie.

Quote context

[...]

- Remember, your mother is at that exact same dance with you. Yeah.

- Right. This could get heavy, Doc.

- Heavy, heavy.

- Marty, whatever happens, you must not let your other self see you! The consequences could be disastrous.

- Excuse me, sir. Yes, you with the hat.

- Who, me?

- Yes.

- Be a pal and hand me a five-eighths inch wrench out of that toolbox.

- Five-eighths? Don't you mean three-quarters?

- Why, you're right.

- I presume you're conducting some sort of weather experiment.

- That's right. How did you know that?

- Oh, I happen to have had a little experience in this area.

- Yes, well, I'm hoping to see some lightning tonight. Although, the weatherman says there's not gonna be any rain.

[...]