27+48

tailwindhome

There's an interesting 'thing' going round on twitter

27 plus 48 is 75

But what's your thought process to get to the answer

Post your answer below (before you read everyone else's)

It's interesting how people process this differently

tailwindhome

For me it's
40+20 = 60
7+8 = 15
60+15 = 75

daniel_b

48 + 20 = 68
68 + 7 = 75

shirley_basso

40+20 = 60
7+8 = 15
60+15 = 75

Pross

TailWindHome wrote:

For me it's
40+20 = 60
7+8 = 15
60+15 = 75

This originally but it may have been because I saw your answer before thinking about it. I went back to it and did 27 + 50 then took off 2.

lesfirth

Daniel B wrote:

48 + 20 = 68
68 + 7 = 75

Simple

pblakeney

TailWindHome wrote:

For me it's
40+20 = 60
7+8 = 15
60+15 = 75

Me too. Probably something to do with the way we were taught.
I find the way these things are done by children these days strange. Different methods, but the same results.

awavey

48 + 2 = 50
27-2 =25

25+50 = 75...

or am I missing something obvious here

tailwindhome

awavey wrote:

or am I missing something obvious here

There's no trick and nothing you're missing.
It's just interesting that people have different thought processes to get the same answer.

briantrumpet

Which buttons to press on the calculator.

Well, no. Did anyone else learn to use those 'calculating machines' where you turned a handle round numbers of times for multiplication? In a maths lesson, before we were allowed to have the fun of using them, we had to do mental calculation to get ballpark figures, because of the risk of jiggling the thing along too far and getting out by factors of something.

Anyway, O-levels done without calculators, but with log tables and slide rules (modern school children don't know what these are).

And the answer to the question... not quite sure, TBH - I think a sort of mixture, dumping the smaller number on top of the bigger one. Calculating VAT at 17.5% in one's head was always fun.

rjsterry

As you posted the answer up, I'm not entirely sure how I would have done it, but I think I would have thought as follows.

Seven and eight is fifteen, carry the ten; two and four is six and one is seven: seventy-five.

Be interesting to try it with two three-digit numbers.

awavey

TailWindHome wrote:

awavey wrote:

or am I missing something obvious here

There's no trick and nothing you're missing.
It's just interesting that people have different thought processes to get the same answer.

some have very complicated thought processes by the looks of it

pblakeney

awavey wrote:

TailWindHome wrote:

awavey wrote:

or am I missing something obvious here

There's no trick and nothing you're missing.
It's just interesting that people have different thought processes to get the same answer.

some have very complicated thought processes by the looks of it

Thing is, everyone thinks their process is the simplest...

Ben6899

This is interesting. I just thought "75" and not sure how I got there!

If I had to help someone figure it out I would probably tell them to work out 30+48 and then knock off the three difference between 27 and 30. Or similar with 27+50...

tailwindhome

rjsterry wrote:

As you posted the answer up

Yeah. I gave the answer as I wanted it to be clear it wasn't a 'trick question' but should have left that out as it maybe skews your natural thought process.

Pross

Ben6899 wrote:

This is interesting. I just thought "75" and not sure how I got there!

If I had to help someone figure it out I would probably tell them to work out 30+48 and then knock off the three difference between 27 and 30. Or similar with 27+50...

Must be a Civil Engineer thing as I did similar but added on 50 and took off 2.

DeVlaeminck

50 plus 27 minus 2

rick_chasey

48 is two under 50 and 27 is two over 15 so cancel each other out - 25+50.

Weird i know. I tend to see the differences between round numbers.

craigus89

I did...

7+48 = 55
55+20 =75

Not sure why but I always seem to do things that way, get the smaller number to a round and then the rest is easy.

Ben6899

Pross wrote:

Ben6899 wrote:

This is interesting. I just thought "75" and not sure how I got there!

If I had to help someone figure it out I would probably tell them to work out 30+48 and then knock off the three difference between 27 and 30. Or similar with 27+50...

Must be a Civil Engineer thing as I did similar but added on 50 and took off 2.

Must be!

rjsterry

Ben6899 wrote:

This is interesting. I just thought "75" and not sure how I got there!

If I had to help someone figure it out I would probably tell them to work out 30+48 and then knock off the three difference between 27 and 30. Or similar with 27+50...

My two primary school age children have been taught "number bonds" - memorising pairs of numbers that sum to each of the integers from 2 to 20, in much the same way as times tables. Possibly you have memorised that 27 + 48 = 75 through repetition, without realising it.

Ben6899

rjsterry wrote:

Ben6899 wrote:

This is interesting. I just thought "75" and not sure how I got there!

If I had to help someone figure it out I would probably tell them to work out 30+48 and then knock off the three difference between 27 and 30. Or similar with 27+50...

My two primary school age children have been taught "number bonds" - memorising pairs of numbers that sum to each of the integers from 2 to 20, in much the same way as times tables. Possibly you have memorised that 27 + 48 = 75 through repetition, without realising it.

It's highly likely. I can't remember to buy milk, but remember various numbers without any issue.

rick_chasey

rjsterry wrote:

Ben6899 wrote:

This is interesting. I just thought "75" and not sure how I got there!

If I had to help someone figure it out I would probably tell them to work out 30+48 and then knock off the three difference between 27 and 30. Or similar with 27+50...

My two primary school age children have been taught "number bonds" - memorising pairs of numbers that sum to each of the integers from 2 to 20, in much the same way as times tables. Possibly you have memorised that 27 + 48 = 75 through repetition, without realising it.

This is certainly how I see it.

I end up half visualising them as shapes that tessellate. 2s match with 8s, 7s with 3s etc.

hopkinb

As per some of the first posters:

20+40=60
8+7=15
60+15=75

Columnar addition in my head I suppose.

Ben6899

Rick Chasey wrote:

rjsterry wrote:

Ben6899 wrote:

This is interesting. I just thought "75" and not sure how I got there!

If I had to help someone figure it out I would probably tell them to work out 30+48 and then knock off the three difference between 27 and 30. Or similar with 27+50...

My two primary school age children have been taught "number bonds" - memorising pairs of numbers that sum to each of the integers from 2 to 20, in much the same way as times tables. Possibly you have memorised that 27 + 48 = 75 through repetition, without realising it.

This is certainly how I see it.

I end up half visualising them as shapes that tessellate. 2s match with 8s, 7s with 3s etc.

This is the driver for how I said I would help someone figure it out. I certainly do this for larger numbers, but as rjsterry suggested... I work with numbers every day - down to mm and 3dp - so I think I simply memorise certain sums, subtractions and multiplications.

Interesting thread, thanks to TWH for starting it off!

rick_chasey

Fast and slow thinking, innit.

herb71

I round up 48 to 50,

50+27=77
77-2 (the rounding difference).

Not very elegant.

rjsterry

Ben6899 wrote:

rjsterry wrote:

Ben6899 wrote:

This is interesting. I just thought "75" and not sure how I got there!

If I had to help someone figure it out I would probably tell them to work out 30+48 and then knock off the three difference between 27 and 30. Or similar with 27+50...

My two primary school age children have been taught "number bonds" - memorising pairs of numbers that sum to each of the integers from 2 to 20, in much the same way as times tables. Possibly you have memorised that 27 + 48 = 75 through repetition, without realising it.

It's highly likely. I can't remember to buy milk, but remember various numbers without any issue.

Repetition, innit. Darts players are very good at adding doubles and triples of 1-20, and subtracting these from 501.

mfin

Ever so slightly different order.

Upon looking immediately the first thing my brain sees the 7 and 8 and knows that's 15, the rest comes after that.

7+8 =15
40+20 = 60
...75

But strangely, I looked at it and immediately thought 75 and all this that followed was just a double check.

pinno

48+22+5.

robert88

Found the biggest divisor of twenty added the remainders.