Clicker Questions - 19-DP-Coins
Question 1: You have three sets of postage stamps: 7-cent stamps, 29-cent stamps and 43-cent stamps. What is the minimum number of stamps that you have to use to have an exact postage of $3.01?
Answer
Think recursively.- If the last stamp is 7 cents, then you'll solve for \$2.94 and add one. Looking at the table, that's $8+1=9$.
- If the last stamp is 29 cents, then you'll solve for \$2.72 and add one. That's $8+1=9$.
- If the last stamp is 32 cents, then you'll solve for \$2.58 and add one. That's $6+1=7$.
- The answer is the minimum of these: 7.
Question 2: With the same stamps as above, what is the minimum number of stamps that you have to use to have an exact postage of $3.05?
Answer
Same process:- $\$3.05 - \$0.07 = \$2.98$. The table says 22 stamps to get \$2.98, so this makes 23 stamps.
- $\$3.05 - \$0.29 = \$2.76$. The table says 24 stamps to get \$2.76, so this makes 25 stamps.
- $\$3.05 - \$0.43 = \$2.62$. The table says 22 stamps to get \$2.62, so this makes 23 stamps.
- The answer is the minimum of these: 23.
Now, before you panic too much, I’m going to give you some help. The following table contains the minimum number of stamps to make each postage amount from \$2.21 to \$3.04 (not including $3.01). This table is a big help!
