Token Drawings
1. **Problem statement:**
We have a bag with 4 red tokens, 3 white tokens, and $b$ blue tokens. We draw three tokens under different conditions (with replacement, without replacement, and simultaneously). We want to find the number of possible drawings and counts of specific color combinations.
---
### Part A: Drawing with replacement
1) Number of possible drawings:
Since each draw can be any of the $4 + 3 + b = 7 + b$ tokens, and draws are independent with replacement, the total number of drawings is:
$$ (7 + b)^3 $$
2) Number of drawings of:
a) Three white tokens:
Each draw must be white, and there are 3 white tokens, so the probability is based on the color only. Since tokens are indistinguishable by color, the count is:
$$ 1 $$ (only one way: white, white, white)
b) Three tokens with the same color:
Possible colors: red, white, blue.
Number of ways:
- Red: 1 way (red, red, red)
- White: 1 way
- Blue: 1 way
Total:
$$ 3 $$
c) No red tokens:
Tokens can be white or blue only, so each draw has $3 + b$ options.
Number of drawings:
$$ (3 + b)^3 $$
d) At least one blue token:
Total drawings minus drawings with no blue tokens.
Drawings with no blue tokens are from red and white only (4 + 3 = 7 tokens):
$$ 7^3 $$
So,
$$ (7 + b)^3 - 7^3 $$
e) The first token is the only red token:
First token is red (1 way), next two are not red (white or blue):
$$ 1 \times (3 + b)^2 $$
f) Only one white token:
White token can be in any of the three positions, others are not white (red or blue):
Number of ways:
$$ 3 \times 4 \times (b) + 3 \times b \times 4 + 3 \times 4 \times b $$
But since tokens are indistinguishable by color and draws are with replacement, the count is:
Number of sequences with exactly one white token:
$$ 3 \times (7 + b - 3)^2 = 3 \times (4 + b)^2 $$
g) Three tokens of three different colors:
Since there are exactly three colors, the only way is one red, one white, one blue in any order.
Number of permutations:
$$ 3! = 6 $$
h) At most one blue token:
Number of drawings with zero or one blue token.
- Zero blue tokens: $7^3$
- Exactly one blue token: Choose position for blue (3 ways), other two from red and white (7 tokens):
$$ 3 \times 7^2 $$
Total:
$$ 7^3 + 3 \times 7^2 $$
---
### Part B: Drawing without replacement
Total tokens: $4 + 3 + b = 7 + b$
1) Number of possible drawings:
Number of permutations of 3 tokens drawn without replacement:
$$ P(7 + b, 3) = (7 + b) \times (6 + b) \times (5 + b) $$
2) Number of drawings of:
a) Three red tokens:
There are 4 red tokens, so number of ways to choose and arrange 3 red tokens:
$$ P(4, 3) = 4 \times 3 \times 2 = 24 $$
b) Three tokens with the same color:
- Red: $P(4,3) = 24$
- White: $P(3,3) = 3 \times 2 \times 1 = 6$
- Blue: $P(b,3)$ if $b \geq 3$, else 0
Total:
$$ 24 + 6 + \max(0, b \times (b-1) \times (b-2)) $$
c) No white tokens:
Tokens are red and blue only, total $4 + b$ tokens.
Number of permutations:
$$ P(4 + b, 3) = (4 + b) \times (3 + b) \times (2 + b) $$
d) At least one red token:
Total permutations minus permutations with no red tokens.
No red tokens means tokens from white and blue only ($3 + b$ tokens):
$$ P(7 + b, 3) - P(3 + b, 3) $$
e) The first token is the only white token:
First token is white (3 choices), next two are not white (red or blue, $4 + b$ tokens), without replacement:
Number of ways:
$$ 3 \times P(4 + b, 2) = 3 \times (4 + b) \times (3 + b) $$
f) Only one blue token:
Choose position for blue (3 ways), choose 1 blue token ($b$ ways), choose 2 tokens from red and white ($4 + 3 = 7$ tokens) without replacement:
Number of ways:
$$ 3 \times b \times P(7, 2) = 3 \times b \times 7 \times 6 = 126b $$
g) Three tokens of three different colors:
Choose one token of each color and arrange them:
Number of ways:
$$ P(4,1) \times P(3,1) \times P(b,1) \times 3! = 4 \times 3 \times b \times 6 = 72b $$
h) At most one blue token:
Sum of permutations with zero or one blue token.
- Zero blue tokens: $P(7,3) = 7 \times 6 \times 5 = 210$
- Exactly one blue token: Choose position for blue (3 ways), choose 1 blue token ($b$ ways), choose 2 tokens from red and white ($7$ tokens) without replacement:
$$ 3 \times b \times P(7, 2) = 126b $$
Total:
$$ 210 + 126b $$
---
### Part C: Drawing simultaneously
1) Number of possible drawings:
Number of combinations of 3 tokens from $7 + b$ tokens:
$$ C(7 + b, 3) = \frac{(7 + b)(6 + b)(5 + b)}{6} $$
2) Number of drawings of:
a) Three white tokens:
Number of ways to choose 3 white tokens from 3 white tokens:
$$ C(3, 3) = 1 $$
b) Three tokens with the same color:
- Red: $C(4, 3) = 4$
- White: $C(3, 3) = 1$
- Blue: $C(b, 3)$ if $b \geq 3$, else 0
Total:
$$ 4 + 1 + \max(0, \frac{b(b-1)(b-2)}{6}) $$
c) No blue tokens:
Choose 3 tokens from red and white only (7 tokens):
$$ C(7, 3) = \frac{7 \times 6 \times 5}{6} = 35 $$
d) At least one blue token:
Total combinations minus combinations with no blue tokens:
$$ C(7 + b, 3) - 35 $$
e) The first token is the only red token:
Since tokens are drawn simultaneously, order does not matter, so this event is not well-defined in simultaneous drawing. The answer is 0.
f) Only one white token:
Choose 1 white token from 3, and 2 tokens from red and blue (4 + b tokens):
$$ C(3, 1) \times C(4 + b, 2) = 3 \times \frac{(4 + b)(3 + b)}{2} $$
g) Three tokens of three different colors:
Choose one token of each color:
$$ C(4, 1) \times C(3, 1) \times C(b, 1) = 4 \times 3 \times b = 12b $$
h) At most one blue token:
Sum of combinations with zero or one blue token.
- Zero blue tokens: $C(7, 3) = 35$
- Exactly one blue token: Choose 1 blue token ($b$ ways), choose 2 tokens from red and white (7 tokens):
$$ b \times C(7, 2) = b \times 21 = 21b $$
Total:
$$ 35 + 21b $$