Number sequence

[landeye]

My 9 year old was asked to predict the next number in a sequence

5, 10, 20, 25, 35, ?

I think the answer is 40 becuse there are 2 sequences going on. 5 +15=20, 20 + 15 =35

Meanwhile 40-15 =25 and 25-15=10

Am I tryng to be too clever.

[rachaelersk]

Yes its 40 i think. here is my logic:-
from 5 to 10 is adding 5 , from 10 to 20 is adding 10, from 20 to 25 is adding 5 and from 25 to 35 is adding 10 so the next number is add 5 and then add 10 and so on....
so add 5 then add 10 alternately. does that make sense?

[jake-the-peg]

This is quite a common 11 plus type question.

I taught my kids to write down the differences and the pattern tends to be clearer:

5---10---20---25---35
....5.....10....5......10

if you see what I mean

[mibn2cweus]

I think jake-the-peg probably has the method of choice but I see another patern. All of the numbers in this sequence are progressive multiples of five skipping every third result. Accordingly 40 would also be the next number in this sequence.

[mibn2cweus]

I misspelled pattern. Sorry, I got too excited.

[butterfly2]

you add 5 and then 10 and 5 and then 10 and so on ...... yes its 40