Math Question???

Question

When I was learning how to drive, I was told that while driving on the freeway I should stay one car
length behind the car in front of me for every 10 miles per hour that I drive. (So, if I were driving 50
miles per hour, I should be 5 car lengths behind). I complained to my dad that this was hard to estimate,
so he gave me an easier rule: just stay 2 seconds behind the car in front of me. Assuming that a car
length is 20 feet and I am traveling 55 miles per hour, how many car lengths behind would I be staying,
using Dad’s 2-second rule?

Answer 1

in 2 seconds at 55 mph you go 55 miles per 60x60 seconds

55/3600 = 55(5,280 ft) per 3600 seconds

= 80 2/3 feet per second

in 2 seconds you go 161 1/3 feet

if a car length = 20 feet, that's about 8 car lengths behind, farther than the 10 per 10 rule

the 20 feet per 10 mph rule would be 5.5x20 feet at 55 mph or 55x20 = 110 feet behind

110/20 = 5.5 car lengths behind at 55 mph