The formula for compound interest is:

Given data:

a. After ten years, that is t = 10 years, the amount in the account will be

b. After twenty years, that is t = 20 years, the amount in the account will be:

c. The time it takes for Harry's initial account value to double will be:

Therefore, the time it takes Harry's initial account to double is approximately 11 years
His model is incorrect because 20 x 7 is not 14, it is 140. If he had 140 instead of 14, he would have been correct.
I haven't done division like that in a long time, so this is what I think it will look like. I didn't add other work (multiplying 4 with #'s) but you can if you have to
Answer:
Ok here is my pro tip:
Step-by-step explanation:
Use both halfs of you brain at the same time, causing you to passout and have your head hit the keyboard, giving you the correct answer
Answer:
#1
Step-by-step explanation: