[Pattern] Solve this Figure Pattern within 5 minutes! | #2

This may seem like a daunting question where the numbers need to be calculated manually. Nope. Let me show you how it's done. To understand how the formula was derived, check out this video: https://www.youtube.com/watch?v=op-O_1f83Hw Question Source: ACS P6 2017 SA1 Q18 Presenter: Kevin Huang Zhenhui Curriculum Specialist, Maths Heuristics P/L