Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length

[MrRoboto75]

You should do all multi/division left to right in the equation.  Same with add/subtract.

[McTraveller]

Priority of mul over div or add over sub doesn’t matter.  It’s helpful to know why: multiplication and division are actually the same thing; addition and subtraction are also the same thing.

Ninjad: I disagree; left to right shouldn’t matter. If it does matter, use parens/brackets.

[Il Palazzo]

You should do all multi/division left to right in the equation.  Same with add/subtract.

What do you mean? It doesn't matter which order you do 2+3+5-1, it'll always come out as 9. Both addition/subtraction and multiplication/division are commutative. As was mentioned above, there's no real difference within each pair. In the former case, you're always adding*, but sometimes you're adding negative numbers. In the latter, you're always multiplying*, but sometimes by fractions.

*(or the other way around, it doesn't matter)

[hector13]

Priority of mul over div or add over sub doesn’t matter.  It’s helpful to know why: multiplication and division are actually the same thing; addition and subtraction are also the same thing.

Ninjad: I disagree; left to right shouldn’t matter. If it does matter, use parens/brackets.

According to a mathematician I watch on the youtoobs, apparently it is important. You do the multiplication and division in order from left to right, then addition and subtraction from left to right.

I’m not sure if this is an American thing though, or if my maths teachers just never went into that level of nuance with it.

[Rose]

The order doesn't matter as long as you understand what the symbols are doing to the numbers. Otherwise it's better to do them left to right.

5-2+3: you don't do 2+3 to get 5, making it 5-5. It's actually 5 + (-2) + 3. Once you have it like this, the order doesn't matter because it's all addition.

Same goes for multiplication and division. 5/2*3 is actually 5 * (1/2) * 3, not 5 / (2*3)

[bloop_bleep]

No, order can definitely matter even with multiplication and division.

For example, 6/2/3 is (6/2)/3, not 6/(2/3).

However when doing math I rarely ever use /, preferring to use fraction notation to be the most clear.

[Il Palazzo]

No, order can definitely matter

Rose's point is well made - if one understands what the notation means, it's unimportant. You'd then never do 6/2/3 as 6/(2/3), because the notation means 6*(1/2)*(1/3), not 6*(1/2)*3. In which case you're free to switch the order to e.g. (1/3)*(1/2)*6.
Otherwise doing left to right is a handy heuristic to keep one out of trouble, I suppose.

[WealthyRadish]

It practical settings where you're computing the result of an expression (computer programming) you would expect most binary operators to have both precedence and left/right associativity. Simple arithmetic operators are generally assumed to be left-associative (evaluated left-to-right when of equal precedence) but other binary operators are typically defined as right-associative. A non-programming example is function composition, e.g. h ∘ g ∘ f is right-associative and evaluated right-to-left.

[McTraveller]

We'd get points taken off in school if we wrote things like 6/2/3, because it can be ambiguous.  Same thing for 5-2+3.  Basically we were taught "no more than one of each type (multiplicative/additive) of operator per expression."  Remember that not all languages are left-to-right.

Incidentally, I wish numbers were written left-to-right, but we kept the Arabic right-to-left.

[Great Order]

The order doesn't matter as long as you understand what the symbols are doing to the numbers. Otherwise it's better to do them left to right.

5-2+3: you don't do 2+3 to get 5, making it 5-5. It's actually 5 + (-2) + 3. Once you have it like this, the order doesn't matter because it's all addition.

Same goes for multiplication and division. 5/2*3 is actually 5 * (1/2) * 3, not 5 / (2*3)

Makes sense. For some reason I'd forgotten that sort of thing applies. I think I'd just gotten so used to having to do that at times that it just sort of floated over my head.

EDIT: New question:

How do we account for genetic variation when sequencing a species' genome? Obviously certain bits don't really mutate because it's vital for life, but there's loads of DNA that does, even if it's silent.

Is there just some sort of "Note that this gene varies" or is it the DNA of a hypothetical organism made up of the DNA of multiple individuals of the species?

[bloop_bleep]

We can sequence one organism's genome. Then we have that one genome which could be enough for our purposes (say extracting a gene for an enzyme). Or like the Human Genome Project we could sequence multiple genomes and be like, "hey so this is pretty conserved but this varies quite a lot."

EDIT: This is good for if you want to see whether something in the genome is actually really important or whether it's something superfluous, because in the former case it would not vary a lot from organism to organism. Reminds that there's a whole huge section of our genome -- I think called non-tandem repeats non-coding tandem repeats -- which is apparently important because it's nearly the same in everyone but we still have little idea what it's for.

[Great Order]

You thinking of non-coding tandem repeats? They don't code anything but they seem to be important in gene expression and regulation, from my understanding.

[None]

Y'know those moisturizing strips on shaving razor heads? Grab your tinfoil hat real quick, but...

D'you reckon they put those there so that it goops up in contact with water, runs into the blades, catches spare hair/skin, then dries, clogging it and making the blade less efficient so you have to buy a new one sooner? Stuff doesn't run through when you rinse it. They don't seem to be particularly useful otherwise.

[EuchreJack]

Y'know those moisturizing strips on shaving razor heads? Grab your tinfoil hat real quick, but...

D'you reckon they put those there so that it goops up in contact with water, runs into the blades, catches spare hair/skin, then dries, clogging it and making the blade less efficient so you have to buy a new one sooner? Stuff doesn't run through when you rinse it. They don't seem to be particularly useful otherwise.

That tracks.

[King Zultan]

Y'know those moisturizing strips on shaving razor heads? Grab your tinfoil hat real quick, but...

D'you reckon they put those there so that it goops up in contact with water, runs into the blades, catches spare hair/skin, then dries, clogging it and making the blade less efficient so you have to buy a new one sooner? Stuff doesn't run through when you rinse it. They don't seem to be particularly useful otherwise.

That tracks.

Damn you Big Razor!