Find the odd one out:21, 11, 26, 6, 36, -4, 46

The correct answer is Option (2) → 46

The terms in the odd places and those in the even places form two separate series, each with its own rule.

• Even places 11, 6, −4: the steps are −5, −10

• Odd places 21, 26, 36, ...: the steps are +5, +10, so the next step is +15

• The last term should be \(36+15=51\), but the series has 46, so 46 is the odd one out