The sequence question shoud be answered by a top-down approach:
- Identify the Sequence Type
- Individuate the logic of sequencing, using analogy both horizontal (subsequent numbers) and vertical (group or parallel, when it is the case)
- Find the lacking number, compliant to sequencing logic
Sequence Types
There are 3 types of sequences:
- Unique: linaer sequence, alone, without combination
- Group: sequence composed by set of fixed lenght
- Parallel: sequence composed by fixed number of intertvined smaller ones
1. Unique
Like: x,y(x),z(x),w(x),...
Identify: unique trend (ascending or descending)
Percentage: about 3/20 of the sequence
Groups are classified by properties, describe in the following 2 (alternative) attributes:
- Patterned: obviously y=y(x), z=z(x), etc
- Double: y=f(x),z=g(y),w=f(z), and so on
2. Group
Like: x,y,z,w,a,b,c,d,i,j,k,l,...
Identify: multiple, fixed size trends
Percentage: about 2/3 of the sequence
Groups are classified by properties, describe in the following 3 attribute:
- Patterned: x,f(x),g(x),h(x) or un-Patterned: x,y,z,w
- by i: indicated the fixed number of number composing the group
- [Simple]|Knot|Chain: providing information about linkage from a group to another
where:
- Simple there are no logical connection from a group to another: x,y,z,w; a,b,c,d
- Knot: the last number of a group drives the the last number of the next one: x,y,z,w(n); a,b,c,d(n)
- Chain: the last number of a group drives the first number of the next one: x,y,z,w; a(w),b,c,d
So, a Grouped Sequence could be expressed by:
[Simple]|Knot|Chain [Patterned] Group by i
It could be identified when there are different trends, among gruop of numbers.
3. Parallel
Like: x,a,i,y,b,j,z,,c,k,w,...
Identify: intertvined trends
Percentage: about 1/5 of the sequence
It is useful to write down the parallel sequences on a paper, like this:
x y z w
a b c d
i j k ...
It could be identified when there are no instant trends.
Accordint to M4Math site, this is the usual distribution of questions:
| Tipe | Percentage |
|---|---|
| Group | 63,16% |
| Unique | 21,05% |
| Parallel | 15,79% |