In basketball, after making a shot, a team may either score two points or three points.
At the end of a game, a team scored a total of 9 2 points. How many different combinations of two-pointers and three-pointers could they have made?
Assume that the team only scored two-pointers and three-pointers (i.e. they did not make any penalty shots).
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Let the number of two-pointers be n , and the number of three-pointers be m . Thus,
2 n + 3 m = 9 2
⟹ 9 2 − 2 n = 2 ( 4 6 − 2 n ) = 3 m
⟹ m = 3 1 ( 9 2 − 2 n )
Also,
n = 2 1 ( 9 2 − 3 m ) = 4 6 − 2 3 m
We see that m must be even. Begin by letting m = 0 :
m = 0 ⟹ 2 n = 9 2 ⟹ n = 4 6
Our first solution ( n , m ) is thus ( 4 6 , 0 ) .
Now, consider another possible number of three-pointers m ′ . Let m ′ = m + 2 . Assume that there is a solution ( n ′ , m ′ ) . Then,
2 n ′ + 3 ( m + 2 ) = 9 2 ⟹ 2 n ′ + 3 m = 8 6 n ′ = 2 1 ( 8 6 − 3 m ) = 4 3 − 2 3 m = n − 3
Thus, any ordered pair ( n ′ , m ′ ) such that n ′ = n − 3 and m ′ = m + 2 , is a solution.
As 4 6 = 3 ( 1 5 ) + 1 , there are 1 5 + 1 = 1 6 possible combinations of two-pointers and three-pointers, when a team has won 9 2 points.
The case 4 6 two pointers and no three pointers is not a combination of the two because in this case the three pointer is absent.
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2a + 3b = 92
Evidently b is even. Let b= 2k.
a + 3k = 46
So k can take any value from 0 to 15 , to be non-negative itself, and yield non-negative a.
16 possibilities.