Move the decimal so there is one non-zero digit to the left of the decimal point. The number of decimal places you move will be the exponent on the 10. If the decimal is being moved to the right, the exponent will be negative. If the decimal is being moved to the left, the exponent will be positive.
This statement is correct as 12 is half of 24 and 2 is half of 4. We can also put this as the fraction 1/2 or 0.5 or 50% or 1:2. Therefore for every one bot there are two girls in the class.
