Question 114535
Joe tossed 4 into the pot. Their average weight was 6 lbs.
You now have 4 objects in the pot with total weight of 4*6=24 lbs
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Then he tossed in 5 more whose average weight was 7 lbs.
You now have 9 objects in the pot with total weight of 24+5*7 = 59 lbs.
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Then he threw in a big one. 
You now have 10 objects in the pot with total weight of 59+x lbs
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The overall average weight of all of them was 7 lbs.
overall average = (59+x)/10
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What did the big one weigh?
EQUATION:
(59+x)/10 = 7
59+x = 70
x = 11 lbs
The big one weighed 11 lbs.
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Cheers,
Stan H.