Step-by-step explanation:
decreasing by 44% means 56% remains . 56% is .56 in decimal
How many half lives ?
.56 = 1/2 ^n log both sides
log .56 = n log(1/2)
n = number of half lives = log.56/ log (1/2) = .8365 halflives
so 260 days is .8365 halflives
260 d / .8365 halflives = 310.8 days per half life