Well every time it gets rid of a shell it grows 1 1/3 times larger. So so to see how much it grows after the first time you say
1 cm * 1 1/3 = 1 1/3 cm
to get the next one you do the same
1 1/3 cm * 1 1/3 cm = 16/9
It will keep going multiplying by 1 1/3. So so we can say in an equation that the
(initial size) * 1 1/3 *(number of shells) = length
Or 1cm * 1 1/3 * n = L
We we know the final length is 10cm
So 1 1/3 * n = 10cm
n = 7.5shells
so approximately 7 or 8 shells
X = 32.5 I believe..........
To figure this equation out, you'll have to divide 39 by 52% (0,52)
39 / 0.52 = 75
39 is 52% of 75 is your answer.
Hope this helps!