Susanna's Challenges - 2

$4*2^{10} = 8*2^n$

$\Rightarrow 2^2*2^{10} = 2^3*2^n$

$\Rightarrow 2^{2+10} = 2^3*2^n$

$\Rightarrow 2^{12} = 2^{3+n}$

$\Rightarrow 12 = 3+n$

$\Rightarrow \boxed{n = 9}$

After 1 second the number of amoebae is 4*2 similarly after 10 seconds i.e full capacity the number of amobae is $4*{ 2 }^{ 10 }$ and so if we start with 8 amobae we will reach full capacity in 9 seconds because $4*{ 2 }^{ 10 }=8*{ 2 }^{ 9 }$