You can use the "e" notation to represent numbers, similar to the E button (not e, but E) on a scientific calculator.

float number1 = 3.31e-8;

this would set number1 = 3.31 * 10^(-8).

The e in the float represents a "times ten to the power of."

This means something like number = 4e5 would represent 4*10^5.

Hope this helps clarify some confusion on cleaning up some of the computation in problem 4.5.

The above post is correct to use %e (instead of %g) in your NSLog to have your answer returned to you in scientific notation (exponential format.)