Magic Stones A3F9F1
1. **Problem Statement:** Majed starts with 2 magic stones. Each time he rubs the stones, every stone produces one new stone. We need to find how many times he must rub the stones to have a total of 100 stones.
2. **Understanding the process:** Initially, Majed has 2 stones.
After 1 rub, each stone produces 1 new stone, so the number of stones doubles.
This means the number of stones after $n$ rubs is given by the formula:
$$ S_n = 2 \times 2^n = 2^{n+1} $$
where $S_n$ is the number of stones after $n$ rubs.
3. **Set up the equation:** We want $S_n = 100$, so:
$$ 2^{n+1} = 100 $$
4. **Solve for $n$:** Take the logarithm base 2 of both sides:
$$ n+1 = \log_2 100 $$
Calculate $\log_2 100$:
$$ \log_2 100 = \frac{\log_{10} 100}{\log_{10} 2} = \frac{2}{0.3010} \approx 6.644 $$
So,
$$ n + 1 = 6.644 \implies n = 5.644 $$
5. **Interpretation:** Since $n$ must be an integer (number of times rubbed), and $n=5.644$ is not an integer, we round up to the next whole number:
$$ n = 6 $$
6. **Verification:** After 6 rubs,
$$ S_6 = 2^{6+1} = 2^7 = 128 $$
which is more than 100 stones.
After 5 rubs,
$$ S_5 = 2^{5+1} = 2^6 = 64 $$
which is less than 100 stones.
Therefore, Majed must rub the stones **6 times** to have at least 100 stones.
**Final answer:**
Majed must rub the stones **6 times** to have 100 or more stones.