the mass of the kitten is given as follows,
m = 90 + 10d
here d = no of days
initially at the time of born
the mass of the kitten is , put d = 0
m = 90 + 10 (0)
m = 90 gm
for double of kitten mass,
2m = 2 x 90 = 180 gm
for 180 gm the no. of days are
180 = 90 + 10d
180 - 90 = 10d
d = 90/10
d = 9 days
so 9 days the kitten will get the double of its mass.
