A basketball player made baskets during a game. Each basket was worth either or points. How many different numbers could represent the total points scored by the player?
- A)
- B)
- C)
- D)
- E)
Answer
E
Key insight
With k three-point baskets the total is 10 + k, and k can be any of 0 through 5, so there are six totals.
Solution
Let be the number of -point baskets, so the other baskets are worth points each. The total is
Since can be or , the possible totals are : six different values, each achieved by exactly one .
The answer is .
Why this works
Every swap of a -pointer for a -pointer raises the total by exactly , so the totals form a run of consecutive integers with one value per choice of . Parametrizing by one count () instead of tracking both kinds is the standard way to make such a "how many totals" question a one-line count.
The trap
Counting only the totals with at least one basket of each kind, or answering 5 because there are five baskets.
Common mistakes
- Counting only the totals with at least one basket of each kind, or answering 5 because there are five baskets.
- Listing through and counting the gaps () instead of the integers themselves.
Techniques
Set up the equation/formula and compute; no special trick needed