Can someone explain this equation (from facebook)?

[NotComingBackAnytimeSoon]

I'm would say the answer to d is 13 and b and c are incorrect. But clearly I'm missing something. Anyone care to explain?

45? I think it's 1x4,+1 then 2x5+2 and so on.

You add the answer to the previous sum.

It shouldn’t have an equals really.

You find the product of the numbers on the left and add the first number so 5 + 8 “=“ 45

Is it something like:

Multiply the second number by the first then add them? Meaning the missing answer is 45?

First answer is 5, then add 5 + 2 to that = 12
Next one 12, then add 3 + 6 to that = 21

Missing answer is 34

I make it 34

As bloody says you add the answer to the previous sum so the answer could be 34 (21+13). However there is potentially a line missing (4+7) and if so the answer would be 21 +11+13 (45).

In reality all these Facebook maths puzzles are deliberately vague to trick you to putting your answer down (and arguments) in the comments to a post that someone has shared from a random page. Once you have commented the page might be able to harvest data about you (depending on your privacy settings). So just don't comment.

See also "bet you can't name a city without an A in it" posts

I got 45. 5 x 8 (+ 5).
All of the previous equations work on this basis, i.e. 3 x 6 (+3) = 21

Yes, someone advised me recently not to answer these types of posts because of data harvesting.

I also come up with 45, as follows:

Actual calculation is 1st number * 2nd + 1st = result

Hence:
14+1 = 5
25+2 = 12
36+3 = 21
58+4 = 45

Having said that, there may be other patterns that work, too. Interestingly, the 1st column of numbers appears to be the fibonacci sequence (minus the duplicate 1 in the beginning).

34?

I didn't realise that about the data harvesting, but I never answer them anyway. I just annoyed me as I didn't spot it immediately, I'm feeling ill and really couldnt be arsed to think about it! Thank you all.

The one about the city without an a is plain stupid! If someone asked me to name a city I'd say London, and that doesn't have an a. It's not exactly tricky!

We should have a thread about these kind of things on MN so we can answer the questions without risk of data harvesting.

Sheffield

34

But I find these things stupid because the numbers don't add.
Working out a sequence of numbers is one thing (it's in all IQ tests), but working out sums that give numbers other than their true results is inane.

Btw, it's not difficult to think of words without a letter. The trick is that you end up focusing on that letter and it becomes more difficult.

I also get 34, but didn't know that the point of these is data harvesting.

I did wonder, because some of the questions like 'name a city with (or without) an A' are obviously so ridiculously easy, but I thought the point was to make stupid people feel clever, ie they would think that they are one of the few who could pass the test.

It's 34. I don't understand why it's set out the way it is.

I was looking into this a bit more after posting and can't find anything definite about data harvesting (although I'm sure I've read that before) but "like farming" is another explanation. www.itgovernance.co.uk/blog/like-farming-and-share-scams-whats-it-all-about basically boosting traffic to a page so it becomes popular and then can be used for spamming feeds.

Either way I make a rule not to comment on posts unless I trust the source page