9514 1404 393
Answer:
8×10⁵ = 800,000
Explanation:
The difference is ...
(4.78×10⁶) -(3.98×10⁶) = 0.80×10⁶ = 8×10⁵
8×10⁵ = 800,000 more people attended at the largest extravaganza.
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Your calculator (or a spreadsheet) can do the subtraction and display the number in whatever format you want.