How the Cijferreeksen test works
Each item is a row of numbers made by a rule, followed by a question mark. You pick the number that comes next from five options. The rule changes from item to item: a fixed step, doubling, two steps taking turns, or two different operations taking turns.
Cijferreeksen is in the MCT-M, the MCT-H and the adaptive MCT-A (where it is called Puzzelen met cijfers). Harver uses the same item type as “Mathematical Reasoning (Number Sequences)”.
How to find the rule
Test the simple rules first, in this order:
- Write the differences between neighbouring numbers. A constant difference is a fixed step.
- If the differences grow fast, try dividing each number by the one before. A constant ratio is a multiplier.
- If the differences alternate, the series uses two steps or two operations in turn.
- If nothing fits, take every second number as its own series. Two series are often woven together.
- Check your rule against every number in the row before you choose.
Worked examples
First: 2, 3, 6, 7, 14, 15, ?. Options: 16, 29, 30, 31, 45. The differences are 1, 3, 1, 7, 1, which do not settle, so look at the operations: add 1, double, add 1, double, add 1. The next step is to double 15, which gives 30.
Second: 20, 3, 18, 6, 16, 9, ?. Options: 7, 12, 13, 14, 15. Taken in order, the row jumps about. Split it: the 1st, 3rd and 5th numbers are 20, 18, 16, falling by 2; the 2nd, 4th and 6th are 3, 6, 9, rising by 3. The missing number is the 7th, so it continues the first series: 14. The trap is 12, the next number in the other series.
Tips for the real Cijferreeksen test
- Thirty seconds is enough for a clear method. Most errors come from a rule that fits only part of the row.
- Note the differences on scrap paper if you are allowed it, rather than holding them in your head.
- If two options both seem to fit, you have probably not checked the rule against the start of the row.
- Skip a series that will not crack. The items get harder, and every right answer counts the same.
Practise Cijferreeksen on CogniPrep
Our Number Series game gives you 30 series on a 15-minute clock, five options each, from easy to hard. Rules include fixed steps, multipliers, alternating steps and operations, and woven series. You can skip. You see your number right and a Lager, Midden or Hoger band against CogniPrep users.