Yeh, I sometimes get funny looks from cashiers when (for example) they charge me $2.87 and I give them $3.12. Then they ring it up and get 25 cents (one quarter) change and you can see the light dawning.
Recently I took a business class, and the teacher started to try to explain the difference between cash accounting and accrual accounting so she could give us the bare bones of how to do a spreadsheet. She had to give it up and start over again when she discovered that half the people in the class had never balanced a checkbook.
Okay, that one I’m going to have to give people, in our plastic world. They probably couldn’t write a cheque, either. On a (mostly) related note, I’ve heard that Canadians use plastic more than any other nation in the world, and don’t our banks love us for it. Cha-ching!
I read this as “I think you should be completely banned…” and thought, “Wow, someone really loves his calculators.”
I was on the math team* in high school, and I have trouble doing simple math in my head. If it’s written down, I can do it, but not when it’s spoken. I need to see the numbers to do the math.
*Number Sense team. 70 math questions ranging from simple addition/subtraction to trigonometry, in order of increasing difficulty, 10 minutes to do as many as possible, no scratch paper or writing anything but the answers down. I was one of the top of my (small) school, but nowhere near the top in the state, and I could do 35+ on a harder test; 45+ on an easier test.
Here (pdf) is a sample of a High School Number Sense test, for the curious. I was wrong; it’s 80 questions.
The rules are as follows:
Number sense is a 10 minutes, 80 problem test. All problems must be solved mentally. Scratch work, erasures, and mark overs are not allowed. A perfect score is 400. Participants receive 5 points for each correct answer and lose 4 points for each problem missed or skipped.
You don’t lose points after the last one you did, so if you did every problem between 1 and 30 except #24, you would lose points for #24, but not for problems 31-80.
Hey Danceswithcats, how do you make the conversion from pressure in a hose, in PSI, to flow rate, in GPM? Is it just a compiled table, for a given nozzle/tip, or is it a function of the total area of the opening at the nozzle tip, or what?
As odd as this may seem, I don’t recall doing that type of conversion in my fluid mechanics class, and you would think it’s a pretty important thing to be able to do.
If you use the fluid - electrical analogy, where pressure = voltage, and flow-rate = current, then you would need to know the “resistance” of the nozzle. Can you dispell my ignorance?
Feel free to email me if you feel the answer is too involved…
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trupa, proud holder of a B.Eng (*Mech, cause I had to use the above analogy to keep current & voltage straight. Oh, that, and, um, complex variables calculus too * :o )
ps. if you post was inronic, then I’ve been whoooshed, becasue it does seem to me like something you should be able to do in your head. Which is why I’m annoyed at myself for not figuring it out right away…
I feel the same way. I got my degree in Pure Mathematics and I can’t do basic arithmetic very fast in my head. I rely on visualizing the operations in my head like I would see on my paper and then they start floating around and switching spots and… where was I?
I find it silly to take immense pride in doing arithmetic in your head at lightning speed. It’s a mechanical skill that can be improved with repetition. Although, there are people out there that are talented in this regard… sort of like natural athletes which are endowed with supreme muscles.
We purposely teach pump ops in a way that is simple. It’s also based on a number of given standards, because the fire service only uses a handful of different hose diameters. Handlines are typically 1 3/4" or 2", you might still see a 2 1/2" blitz line, and supply lines are usually 5". I’ve always taught people to work from the nozzle backwards.
Ex: If we want the handline deployed to flow 200 GPM, and the device stat sheet says it needs 200 PSIG presented to achieve that flow, then I start with 200, and add the known friction loss per 100’ of supply line, (let’s say it’s 10#), and the prepacked crosslay is known to 250’, that means I have 25# friction loss, which is added to the starting 200, so my discharge pressure for that line would be 225PSIG.
If my compound gauge read 160PSIG static (hydrant pressure) and opening that one line caused a drop of 40PSIG, then I could safely open two more lines of equal size, and still maintain 40PSIG residual pressure as a safety margin.
Conversely, if I was on a lousy hydrant, started at 90PSIG and dropped 60PSIG with that one handline in service, I can’t feed any more and need to warn other pumpers to find a different portion of the water grid so we don’t starve one another.
Most of us dinosaurs who were educated in the years before calculators learned to “make change” by counting up from the amount due to the amount received.
Item for $10.47, received $20 bill:
"That’s 10.47, 48, 49, 50 [3 pennies dispensed], 75 [quarter dispensed], eleven [another quarter], twelve, thirteen, fourteen, fifteen [four ones dispensed], twenty [five dollar bill dispensed]. "
No math involved, just counting.
I cannot do simple arithmetic of more than about 2 digits without writing it down. Even then, on a long column of numbers, especially 3- or more digits, I’ll probably get it wrong.
My daughter, OTOH, of whom I am very proud, figured out the 12 times tables before she was five. We were in the supermarket passing the dairy aisle and she saw a box of a dozen eggs. “What’s a ‘dozen?’” (Yes, she could read already.) “Well, that means twelve of something.” “Oh.” Pause. “Then,” she said, “Two dozen would be twenty-four.” “Right.” I am stunned. “And three dozen would be thirty six.” “Um, yeah.” She kept going until she got up to the three-digit answers before stopping. By that time I was gripping the cart so hard my knuckles were white. When she got home, she got people to help her get up to 12 X 12. Later on, when she was too big to sit in the cart, she used to pick up the discarded tickets at the deli section and add the numbers up in her head **for fun. **
Yup. I created my own alphabet when I was around 9 or 10, and talk myself to write in it just for fun. There are definitely mathematic and linguistic people out there.
No calculators available when I was in school; not even in college. I’ve never been able to do much more than simple math in my head but I’m shocked at people today who can’t make change.
I have a dim memory of reading an interview with some physicist whose name escapes me. He had an uncanny ability to do math mentally and when asked to explain how he did it, he said it was simple—he just visualized a slide rule and worked out the answer.
Ah, many thanks Danceswithcats, I understand. You just make sure you deliver the pressure required to acheive the documented flow rate at the nozzle tip, without worrying about any changes to the flow rate. Even easier.
My apologies to the non-math folks here for this highjack.
