Coin Probability
1. **State the problem:**
Anna has 2 coins totaling 30p, and Tom has 4 coins totaling 30p. We want to find who is more likely to pick a 10p coin from their respective bags.
2. **Analyze Anna's bag:**
Let the number of 10p coins Anna has be $x$. Since she has 2 coins total, the other coin's value is $30 - 10x$ pence.
Possible values for $x$ are 0, 1, or 2.
- If $x=0$, total value would be less than 30p (impossible).
- If $x=1$, the other coin is $30 - 10 = 20$p (a 20p coin).
- If $x=2$, total value is $2 \times 10 = 20$p, which is less than 30p (impossible).
So Anna must have exactly one 10p coin and one 20p coin.
Probability Anna picks a 10p coin is:
$$P_A = \frac{1}{2} = 0.5$$
3. **Analyze Tom's bag:**
Tom has 4 coins totaling 30p. Let the number of 10p coins be $y$.
The total value of the 4 coins is:
$$10y + \text{value of other coins} = 30$$
Since coins are standard UK coins, possible coins are 1p, 2p, 5p, 10p, 20p, 50p, etc. But since total is 30p with 4 coins, and 10p coins are involved, let's consider possible $y$ values.
- If $y=0$, other 4 coins total 30p.
- If $y=1$, other 3 coins total 20p.
- If $y=2$, other 2 coins total 10p.
- If $y=3$, other 1 coin total 0p (impossible).
- If $y=4$, total 40p (too high).
Try $y=1$:
Other 3 coins total 20p, possible with 5p, 5p, 10p or 10p, 5p, 5p, but that would increase 10p coins.
Try $y=2$:
Other 2 coins total 10p, possible with 5p and 5p.
So Tom likely has 2 coins of 10p and 2 coins of 5p.
Probability Tom picks a 10p coin is:
$$P_T = \frac{2}{4} = 0.5$$
4. **Compare probabilities:**
$$P_A = 0.5, \quad P_T = 0.5$$
Both Anna and Tom are equally likely to pick a 10p coin.
**Final answer:** Both equally likely.