A student estimated the sum
7.95 + 8.11 + 78.5 + 8.05 + 79.4 + 0.815 as:
All the numbers begin with a 7 or 8, so use cluster estimation.
8 + 8 + 80 + 8 + 80 + 0.8 = 184.8
Explain why this reasoning is not accurate.
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