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Carl912 · Mar 10, 2009, 12:48 PM

Need to find the next number in the following sequence
1 1/2 5 10 1/2 18
I am so very confused...
Please help!

kim_of_the_shoe · Mar 10, 2009, 02:58 PM

Is it 1 1/2, 5, 10 1/2, 18? It was a bit hard to work out at first from the way it was set out but I think I know how to work it out.
Firstly you have to find the difference between each number. In this case the difference changes each stage. These are the dirrences between each number:
3 1/2 5 1/2 7 1/2
As you can see the numbers increase by 2.
To work it out from here you treat this as a second sequence which goes up in 2's.
To find the next few terms simply at 2 to the last difference of the second sequence, then add this to the first sequence.
For instance, the next number in the first sequence will be 18 + 9 1/2 and then the number after that will be the product of the sum above + 11 1/2 and so on...
Hope this helped :)

Carl912 · Mar 11, 2009, 04:33 AM

Originally Posted by kim_of_the_shoe

is it 1 1/2, 5, 10 1/2, 18? It was a bit hard to work out at first from the way it was set out but i think i know how to work it out.
Firstly you have to find the difference between each number. In this case the difference changes each stage. These are the dirrences between each number:
3 1/2 5 1/2 7 1/2
as you can see the numbers increase by 2.
To work it out from here you treat this as a second sequence which goes up in 2's.
To find the next few terms simply at 2 to the last difference of the second sequence, then add this to the first sequence.
For instance, the next number in the first sequence will be 18 + 9 1/2 and then the number after that will be the product of the sum above + 11 1/2 and so on ...
Hope this helped :)

thank you kim!