How do you write 1.8 trillion in scientific notation?

To write 1.8 trillion in scientific notation, you first express it as 1.8 multiplied by 10 raised to the power of 12. This is because "trillion" corresponds to 12 zeros (1,000,000,000,000). Therefore, 1.8 trillion in scientific notation is (1.8 \times 10^{12}).