Here's how we get there:

* Move the decimal point: Start with the number 72,000,000. Move the decimal point 7 places to the left so that you have a number between 1 and 10 (in this case, 7.2).

* Exponent: The number of places you moved the decimal point becomes the exponent of 10. Since you moved it 7 places to the left, the exponent is 7.

Therefore, 72,000,000 in scientific notation is 7.2 x 10⁷.