Problema Solution
During the first four days of thus week, katie and her friends together ate an average of 8 cookies a day. If the cookies they ate on the fifth day are included, together they ate an average of 10 cookies a day for the five days. How many cookies did they eat on the fifth day?
Answer provided by our tutors
let
x = the total number of cookies eaten in the first 4 days
y = the number of cookies eaten on the fifth day
x/4 = 8
x = 4*8
x = 32 cookies
together they ate an average of 10 cookies a day for the five days
(y + x)/5 = 10
(y + 32)/5 = 10
by solving we find:
y = 18 cookies
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They ate 18 cookies on the fifth day.