let it's original weight be x lbs
after 1 hour it weighed 2/3 x lbs
after 2 hours it weighed (2/3)(2/3)x lbs
4/9 x = 40
x = 40(9/4) = 90 lbs
A block of ice loses one third of its weight every hour. After 2 hours, the block weighs 40 pounds. How much did the block weigh to begin with?
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