Arrange $3.2\times 10^{-5},9.1\times 10^{-6}$ and $4.7\times 10^{-5}$ from smallest to largest.

Compare the powers of ten first: $10^{-6}$ is smaller than $10^{-5}$, so $9.1\times 10^{-6}=0.0000091$ is the smallest. Then compare the decimal parts of the two $10^{-5}$ numbers: $3.2<4.7$. The trap is calling $9.1\times 10^{-6}$ the largest because 9.1 is the biggest decimal part.