# Arithmetic

Discussion in 'Personal' started by lilachardy, Feb 15, 2016.

1. ### lilachardyStar commenter

I am increasingly horrified and astounded by the number of spammy posts on Facebook along the lines of
7 - 4 + 3 x 0 + 1 = ?

3 - 3 x 6 + 2 = ?

Where THOUSANDS of people have posted their answer, and most of them are wrong. I expect bottom set students to get this sort of thing right, and quickly too.

I don't know why I'm posting this here. I just needed to vent my frustration with standards in society!

Try the maths quiz in today's Guardian.

3. ### HelenREMfanStar commenter

Gosh we must have nothing better to do then.... and the answers are ... ?

It's a bit of a teachery trick question though, because of the assumption about order-priority given to multiplication.

5. ### lilachardyStar commenter

In what way is it trickery? It's just fact.

6. ### bombaysapphireStar commenter

There is no assumption about order-priority, just a clear set of rules. Nothing about trickery. More about clarity and consistency.

lilachardy likes this.

Of course there is! If you don't do the multiplication first you get a different answer!

8. ### lilachardyStar commenter

In what way is that a trick?
If you do it wrong you get the wrong answer....true in many situations, but not a trick.

9. ### bombaysapphireStar commenter

Of course you get a different answer if you don't do the multiplication first. The fact that you do multiplication first isn't an assumption. It is a rule.

10. ### lilachardyStar commenter

Helping your Uncle Jack off a horse.
Helping your uncle jack off a horse.

Different results there - is that a trick?

Eureka! likes this.

I know it's the rule.. but people don't normally do arithmetic by using expressions. Most people will only meet such an expression in school rather than real life. So it's not quite such an indictment of popular arithmetic that Lilac is making out, IMOSHO.

12. ### lilachardyStar commenter

Erm no - that rule applies to every single calculation you do, even in 'real life'.

Think about it - your example is written out as an expression. People don't do that in real life. The rule is not needed in RL by most because, for most, there is nothing written out , or if it is, it will be an idiosyncratic concoction of numbers and subcalculations that they jot down, not a proper expression.

14. ### lilachardyStar commenter

Okay, I see what you're getting at.
But are you not shocked that people can't perform simple calculations correctly?

15. ### bombaysapphireStar commenter

I am still struggling to understand why you described the correct method as
.

16. ### Vince_UlamStar commenter

It's like you've never shopped for groceries.

17. ### LascarinaStar commenter

Don't we all? Apart from one or two notable exceptions.

It would be interesting, Lilac, to know if most of the wrong answers are "right " if the operator priorities follow different precedence rules - e.g. first come first served....

19. ### phlogistonStar commenter

A cheap calculator (which must be right) will give a different answer to a mathematician.
Truth is, when I learnt the numbers, they just went in and it was no effort at all. I'm now realising just how hard and unintuitive some folk find numbers.

20. ### lilachardyStar commenter

Some of them.