Final answer:
The bank account balance grows by a factor of 2 in 16 years and by a factor of 4 in 32 years.
Step-by-step explanation:
The doubling time of a bank account balance is 8 years. To find the factor by which it grows in 16 years, we divide 16 by 8. Therefore, the factor is 2 times.
To find the factor by which it grows in 32 years, we divide 32 by 8. Therefore, the factor is 4 times.