# Mumsnet Talk

Please note that threads in this topic are removed from the archive 90 days after the thread was started. If you would like your thread to be retrievable for longer than that, please choose another topic in which to post it.

## Maths question help

(131 Posts)
itshardthinkingofanickname Tue 25-Feb-14 21:10:38

A bat and a ball cost £1.10 in total. The bat costs £1 more than the ball. How much does the ball cost?

Tue 25-Feb-14 21:11:41

5p. Cheap ball!

TheBuskersDog Tue 25-Feb-14 21:11:52

10p

dilbertina Tue 25-Feb-14 21:12:22

umm - is this a trick? 10p?

Tue 25-Feb-14 21:12:23

5p?
So ball is 5p + bat 105p = 110p

TheBuskersDog Tue 25-Feb-14 21:13:16

Oh no, 5p

NickNacks Tue 25-Feb-14 21:13:50

Agree 5p

dilbertina Tue 25-Feb-14 21:14:29

ok 5p!

contortionist Tue 25-Feb-14 21:14:56

x + y = 110
x - y = 100

2x = 210

Divide by 2:

x = 105

And back substitute to get y = 5. Bargain.

itshardthinkingofanickname Tue 25-Feb-14 21:15:02

I was watching a programme last night about how we think and make decisions.

All to do with cognitive bias.

Half of Harvard students used their fast brain and said 10p.

Will post more examples - fascinating to see how we think and don't see what is there.

Marcipex Tue 25-Feb-14 21:15:12

I would have said 10p but heymammy has convinced me it is 5p.

itshardthinkingofanickname Tue 25-Feb-14 21:16:19

This one:

You might know this one - but it has important real life implications.

itshardthinkingofanickname Tue 25-Feb-14 21:18:34

You see cognitive bias on here - and no doubt in your work place.

Selective attention = people can be so focussed on one task they fail to notice what's going on around them. A New York cop was jailed because he was chasing a suspect and did not see 2 cops near him beating someone up. His brain just didn't see it.

NickNacks Tue 25-Feb-14 21:19:07

Hmm I counted 15 and did see it!;)

Marcipex Tue 25-Feb-14 21:20:15

I counted 11 passes, knew something was odd and didn't know what!

MirandaWest Tue 25-Feb-14 21:21:15

itshardthinkingofanickname Tue 25-Feb-14 21:21:47
itshardthinkingofanickname Tue 25-Feb-14 21:24:02

"Confirmation bias is the tendency to look for information that confirms what we already know. It's why we tend to buy a newspaper that agrees with our views. There's the hindsight bias, the halo effect, the spotlight effect, loss aversion and the negativity bias.

This is the bias that means that negative events are far more easily remembered than positive ones. It means that for every argument you have in a relationship, you need to have five positive memories just to maintain an even keel."

Confirmation bias was interesting - they asked some NSA analysts to analyse data and they seemed to use data that confirmed their inital thoughts rather than looking at all the data.

itshardthinkingofanickname Tue 25-Feb-14 21:25:06

" It means that for every argument you have in a relationship, you need to have five positive memories just to maintain an even keel."

That's interesting - looking back on my relationship, the arguments stand out more.

NanetteCarter Tue 25-Feb-14 21:26:02

cognitive I didn't form a pair of simultaneous equations - I just did a single linear equation with one variable. Is there a 'right way' to do these?

cost of ball = x
cost of bat = x + 1
total cost = x + x + 1 = 2x + 1 = 1.10
2x = 1.10 = 1 = 0.10
x = 0.05!

itshardthinkingofanickname Tue 25-Feb-14 21:27:14

Was that your fast or slow brain

itshardthinkingofanickname Tue 25-Feb-14 21:29:12

Ok - this one

An individual has been described by a neighbor as follows: “Steve is very shy and withdrawn, invariably helpful but with very little interest in people or in the world of reality. A meek and tidy soul, he has a need for order and structure, and a passion for detail.” Is Steve more likely to be a librarian or a farmer?

LowCloudsForming Tue 25-Feb-14 21:29:18

Silly question but why does the ball have to cost 5p? Could it not cost 0p, 1p, 2p, 3p, 4p? Then the bat would cost £1.10, £1.09 etc.

I think the original question is about semantics.

Tue 25-Feb-14 21:29:27

My very very first though was 10p but was immediately followed by ooh! no that doesn't work!

I can totally believe in the cognitive bias, I think I've read about it before and it's because our brains are being a bit too clever and trying to save time/processes so go for the obvious choice every time.

itshardthinkingofanickname Tue 25-Feb-14 21:31:59

The bat and ball cost £1.10 together.

So if the bat is £1 more than the ball, the ball costs 5p and the bat £1.05

No semantics there.

Linda is thirty-one years old, single, outspoken, and very bright. She majored in philosophy. As a student, she was deeply concerned with issues of discrimination and social justice, and also participated in anti-nuclear demonstrations...The respondents are asked to rank in order of likelihood various scenarios: Linda is (1) an elementary school teacher, (2) active in the feminist movement, (3) a bank teller, (4) an insurance salesperson, or (5) a bank teller also active in the feminist movement.

### Join the discussion

Registering is free, easy, and means you can join in the discussion, get discounts, win prizes and lots more.

Register now