Three of the following four number groups are alike in a certain way. Choose the one that does not belong to the group.
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → 15 – 20 – 26
Find the difference between neighbouring numbers in each group.
Option (1) 7 – 12 – 19 — 12 − 7 = 5 and 19 − 12 = 7: gaps +5, +7.
Option (2) 11 – 16 – 23 — 16 − 11 = 5 and 23 − 16 = 7: gaps +5, +7.
Option (3) 5 – 10 – 17 — 10 − 5 = 5 and 17 − 10 = 7: gaps +5, +7.
Option (4) 15 – 20 – 26 — 20 − 15 = 5 and 26 − 20 = 6: gaps +5, +6.
Three groups go +5, +7; 15 – 20 – 26 goes +5, +6, so it is the odd one out.