Dow 'giant chalkboard' by DraftFCB Chicago

The chalkboard began to reveal an elaborate equation that combines mathematics with numbers that are significant to scientific human achievements throughout history.

As the painters wrote out the mathematical poem over four days, a banner read: "Solutionism. The new optimism."

Throughout the execution, maths enthusiasts and passers-by were invited to participate and guess portions of the equation through a website and the Twitter handle @giantchalkboard, which provided clues and prompts to the significance of the numbers. On the fifth day, the answer was revealed to be seven billion, which represents the soon-to-be world population.