Question

the Times of sarah's first swim lengths are 27 seconds ,35 seconds ,and 31 seconds. in how many seconds must length four be completed so the mean is 30 seconds

Answer 1

Length four must be 27 seconds.
Mean=x1,x2,x3,x4/n
30=27+35+31+x4/4
30*4=93+x4
X4=120-93=27