Explained per part › Number series
Number series
You see a row of numbers and find the next one. Behind every series there is a rule: adding, multiplying, alternating or a known series such as squares.
The Dutch Armed Forces, the Dutch capacity test, Korn Ferry (logical) and many other ability tests. Also in the IQ test on this site.
How to solve it
Series: 3, 6, 12, 24, ?
- Write down the differences: +3, +6, +12. They are not equal.
- The differences double. So look at the ratio: 6 ÷ 3 = 2, 12 ÷ 6 = 2.
- Rule: × 2 each time.
- 24 × 2 = 48.
Answer: 48.
Try it yourself
1. 2, 5, 11, 23, ?
- 46
- 47
- 35
- 48
Show the answer
B. Each time × 2 + 1: 2 → 5 → 11 → 23 → 47.
2. 4, 9, 7, 12, 10, ?
- 15
- 13
- 8
- 17
Show the answer
A. Alternating + 5 and − 2: 4 +5 = 9, −2 = 7, +5 = 12, −2 = 10, +5 = 15.
3. 1, 4, 9, 16, 25, ?
- 30
- 36
- 49
- 35
Show the answer
B. Squares: 1², 2², 3², 4², 5², so 6² = 36.
Tips
- Write the differences under the series. If they are not equal, look at the differences of the differences, or at × and ÷.
- Does the pattern alternate? Then look at the odd and even positions separately.
- Know the familiar series: squares, powers of 2, prime numbers, Fibonacci.
Practise with new questions: Number series
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