Write 1.23 x 10–4 in standard notation

Rule:

1.  If the exponent of 10 is positive, move the decimal to the RIGHT
    that number of places and remove the ×10exponent

2.  If the exponent of 10 is negative, move the decimal to the LEFT
    the absolute value of that number of places and remove the
    ×10exponent

In 1.23 x 10–4, the exponent is negative, so we take the 
absolute value of -4, which is 4, and move the decimal of 1.23 four 
places to the left. To do that we need to put three 0's in front, 
so the answer is

    .000123

Edwin