“I already have the approximate answer in mind before I enter any numbers.”
That’s the beauty of exponential notation and mental math. Here’s an example: suppose you have a problem: (450,214 * 190) / (1,082,410)
Round the 190 up to 200 and break that down to 2 * 100.
Then the numerator is 2 * 450,000 (rounded down) which is 900,000. Multiply that by the 100 and you have 90 million.
Alternatively, you could round the 190 up to 1,000, multiply that by the 450,000 and get 450 million. Divide that by 5 and you get 90 million.
Then round the denominator down to 1 million.
Rough answer: 90 million divided by 1 million is 90.
Or 4.5 E 5 * 2 E 2 / 1.1 E 6 = (4.5 * 2) E 7 / 1.1 E 6 = (9 / 1.1) E 1 ~ 90
Actual answer is 79.02. But, by doing the quick calc to get 90, you know what ballpark you should be in. This is where the county assessor and all of his or her colleagues failed.
I remember about fifth grade (1963) reading a Popular Science article about “mental math” and being intrigued by it. It stuck with me all my life!
“””I remember about fifth grade (1963) reading a Popular Science article about “mental math” and being intrigued by it. It stuck with me all my life!”””
I am a few years older than you, but I remember when I was about in the fifth grade developing a system to multiply two numbers—such as 36 times 28-—in my head. No longer have that talent!!!