Can YOU solve this sequence?

(35 Posts)
caraway Mon 01-Oct-12 19:15:41

There's a chocolate prize up for grab- a tin of Celebrations- and I'm desperate for help. It goes- 100, 200, 400, 800, 1500. If only there wasn't the 1500. I've tried everything- adding then dividing, multiplying, seeing if it jumps. Anyone know the answer, or could give ideas on how to do it? The 'homework' is a parent's competition- the form actually said 'you can use outside help'. If you know the answer, can you give advice on how you got it instead of telling me the answer (I want to know how it's done, not just know the answer).

TwinMummy30 Mon 01-Oct-12 19:48:39

oops wrong! just saw it 400+900 isnt 1500 blush

Shelium Mon 01-Oct-12 19:54:17

100
200
400 = 200 (previous number) + 100 (number before that) +100
800 = 400 (previous number) + 200 (number before that) +200
1500 = 800 (previous number) + 400 (number before that) +300

? = 1500 (previous number) + 800 (number before that) +400 = 2700
?? =2700 (previous number) + 1500 (number before that) +500 = 4700

caraway Mon 01-Oct-12 20:16:36

So is it Shelium or WillieWaggledagger? If it's WillieWaggledagger, I think it would be 2600 and 4200. Or Shelium. Or the running track. I think it's meant to be math-sy, but I'm not sure. Do you think I could ask if it's meant to be maths-based or anything?

They really should have given just one more number! grin

richmal Tue 02-Oct-12 16:36:04

Message withdrawn at poster's request.

richmal Tue 02-Oct-12 16:50:11

Oops, You did not want the answer. I will ask for it to be deleted.

Basically, look for the gaps in the gaps in the gaps.

arkestra Tue 08-Jan-13 15:44:39

http://oeis.org/search?q=100%2C+200%2C+400%2C+800%2C+1500&language=english&go=Search

arkestra Tue 08-Jan-13 15:45:33

(Kind of a blunderbuss approach - but if it's in a sequence you will find it here!)

arkestra Tue 08-Jan-13 15:48:54

(and now I realise I've woken a zombie thread, never mind)

alanyoung Sat 02-Feb-13 19:34:26

Did you ever find the answer?

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