Anne scored 75, 81 ,77 , and 83 in her four tests. what score should she get in her fifth test to have an average of 80?

Remark

You set this up as (75 + 81 + 77 + 83 + x)/5 = 80      Combine the left

(316 + x)/5 = 80                                                           Multiply by 5

316 + x = 80 * 5

316 + x = 400                                                              Subtract 316

316 - 316 + x = 400 - 316

x =  84  <<<< Answer

e^-kt = n/n0 = 0.79  

-kt = ln 0.79  

t = - ln 0.79/0.0001  

= 2357 years

step-by-step explanation: