Scientific Notation
giving : 7.42000 x 100+5
or 7.42 x 105 
The decimal point must be moved to the left. 
742,000. x 100
(3).  
Alternately, begin with:
7.42 x 105
The number of places the decimal point must be moved so that the notation is in the correct form:
(2).
Value of the exponent?
exponent of 10 is a  positive whole nb.
(1).
a number greater than 1:
    742,000
•
For each place the decimal point is moved to the left add 1 to the original exponent of 10