I’m no expert, but hopefully these ideas help a little.

1. I memorized these numbers below (chart)

2. I rarely divided by 60 minutes, but instead I tried to think in fractions.

3. For the examples I used 'easy' numbers to keep this simple. if you get a decimal I would round and estimate.

4. hopefully my math is correct and I haven't embarrassed myself

5. Guess and check is important for deciding what fraction to use

Minute(s) Occurrences per hour

1 60

2 30

3 20

4 15

5 12

6 10

10 6

12 5

15 4

30 2

60 1

For the fraction system to work you are looking for a common denominator.

Simple example

Say the AC is travelling at 200mph for 90 min. How far did it go?

90 min = 1 ½ hours. 1 hour = 200 miles. 30 min = 100 miles. 200 + 100 = 300 miles in 90 min.

example 2:

AC travels at 156mph for 75 minutes. How far did it travel?

75 min = 15 minutes x 5

15 minutes happens 4 times per hour, so

156/4= 39miles

This means that every 15 minutes the AC travels 39 miles.

15 min happens 5 times in 75min. So 39 x 5 = distance.

To make this easier, do 40 x 5 = 200, but subtract 5 (because 40 – 39 = 1 x 5 = 5)

and you get 195 miles.

example 3:

AC travels 250miles in 40 min. What is its speed?

Divide each by 10.

250 miles/10 = 25 miles. 40 min / 10 = 4 min

Therefore every 4 minutes the AC travels 25 miles.

4 minutes occurs 15 per hour, so multiple 25 x 15.

For mental math, instead of 25x15, try (25x10 = 250) + (25x5 = 125) = 375mph

** I didn't think of this. I stole the idea from a MARS officer

***** Edited several times because I'm bad at proof reading.