series = 50, 60, 72...
a = 50 r = 1.2
the 8th zoom is the 9th term.
tn = ar^(n-1)
t9 = 50 x 1.2^8
= 214.99 mm = 215mm
ii)tn = ar^(n-1) = >400
50 x r^x = 400 ..... x = n-1
r^x = 8
1.2 ^ x = 8
log(1.2)8 = x
x = log 8
/log1.2
= 11.40
therefore it will...