Question 1126434
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a)  The equation is  N = N(t) = {{{400*(1+0.05)^t}}} = {{{400*1.05^t}}},

    where t is the time in hours from the starting moment.




b)  . . . after one hour ?

    To answer this question, substitute t= 1 into the formula and calculate.



    . . . after four hours ?

    To answer this question, substitute t= 4 into the formula and calculate.
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You may use your calculator.  


Happy calculations !