An investment of …100 increased to …1000 have increased to $8000 by…

An investment of $100 was made in a certain account and earned interest that was compounded annually. The annual interest rate was fixed for the duration of the investment, and after 12 years the $100 increased to $400 by earning interest. In how many years after the initial investment was made the $1000 have increased to $8000 by earning interest at that rate?

This problem repeats another one in the library (at most with different numbers), so it's left out of browsing.

AQuA-RAT — Algebra Question Answering with Rationales (Ling et al., DeepMind, 2017) · train #34068