Element Changes — Add, Remove, Replace

🎯 Learning Objective

Crack series where the number or type of elements changes each step, including two rules running together.

💡 Concept

• First COUNT the elements in every frame: counts like 3, 5, 7 reveal an add-2 rule → next frame has 9
• Elements may be added at a fixed position each time — e.g. a new dot appears 90° clockwise from the last one
• Replacement rule: the OLDEST element leaves and a new one enters (first-in, first-out) — watch which element is senior-most
• Many series run TWO rules at once, e.g. the arrow rotates 90° while one dot is added — verify each rule separately
• Type changes also cycle: circle → square → triangle → circle repeating every three frames

✏️ Easy Example

Q. Frame 1 has a dot at 12. Frame 2 has dots at 12 and 3. Frame 3 has dots at 12, 3 and 6. What does frame 4 show?

1. One dot is added each step
2. Each new dot appears 90° clockwise from the previous new dot

Answer: Dots at 12, 3, 6 and 9

🇮🇳 Real-Life Example

Diwali chaser lights: every second one more bulb glows along the string, always the next one in line — an add-one-element series running on your balcony.

📝 Exam-Level Example

Q. In a series, frames contain 2, 4, 6 and 8 line segments. Also, a shaded corner moves one corner clockwise each frame from the top-left. Describe frame 5.

1. Counts +2 each step → frame 5 has 10 segments
2. Shading: top-left → top-right → bottom-right → bottom-left → back to top-left

Answer: 10 segments with the top-left corner shaded

📝 Exam-Level Example

Q. Frames show these shapes in order: circle-square, square-triangle, triangle-circle. Which pair comes next?

1. Each shape moves one step in the cycle circle → square → triangle
2. triangle → circle and circle → square

Answer: circle-square (the cycle restarts)

🪄 Memory Trick

Run the C-P-T scan on every frame: Count of elements, Position of each, Type of each. Whichever of the three changes steadily IS the rule — and if two change, you have two rules.

⚠️ Common Mistakes

• ❌ Catching the rotation rule but missing the second rule (an element quietly added each frame)
• ❌ Assuming the newest element is replaced when the series actually removes the OLDEST
• ❌ Matching options by overall look instead of verifying the exact element count

🏆 Exam Tips

• ✅ Write the element count above every frame before anything else — it is the fastest rule to spot
• ✅ Eliminate options whose count is wrong, then test position and type on the survivors

📌 Summary

• Count first: steady +1/+2 counts crack most series
• Replacement follows first-in-first-out — oldest leaves
• Two rules often run together; verify each separately
• C-P-T scan: Count, Position, Type