In the flexyourrights link, they advise you to say no if you’re asked if you know how fast you were going.
I always thought that saying you didn’t know how fast you were going could be taken as an admission of reckless driving, and that they ask that question because if you were actually speeding it’s a catch-22.
I’ve had the pleasure of speaking with far too many officers on the side of the roadways. Here’s my boilerplate answer to this question. ‘Do you know how fast you were going?’
Depending on the situation either:
I don’t know my exact speed because I was concentrating on keeping with the flow of traffic.
or
I believe I was traveling close to the posted speed limit.
Neither answer admits guilt and both answers relay to the officer your intent to travel safely.
A more commonly asked question is ‘do you know why I pulled you over’ and a simple ‘no sir’ will suffice.