You learned in Activity 2 the power of compound interest. Interest is the price paid for the use of someone else's savings.
Compound interest is interest earned on saving that includes previously earned interest.
Tommy withdraws his interest each year and uses it to buy himself something special. For Suzy For Tommy Suzy keeps her interest in her account. Remember, Tommy does not leave any of the interest in his account. Now consider how much Suzy and Tommy will have in their accounts after 20 years. Suzy earned more money because her interest was compounded.