Choice A is the correct answer. Find when users reach 100,000.

1. Formula: $U(t) = 10000(1.30)^t$, solve for $100000 = 10000(1.30)^t$.
2. Simplify: $(1.30)^t = 10$.
3. Test:
   • $t=8$: $(1.30)^8 \approx 8.157$ (below 10)
   • $t=9$: $(1.30)^9 \approx 10.604$ (above 10) ✓
4. Answer: Between 8 and 9 months.

💡 Strategic Tip: Test integer values to bracket the answer.

Choice B is incorrect because growth happens faster. Choice C is incorrect because$(1.30)^6 \approx 4.83$. Choice D is incorrect because it exceeds 100,000 before month 10.