Help.I need to ace this.

45 was divided by a power of ten to get 4.5. what power of ten was it divided by? people 4.5

The area (a) of a circle with a radius of r is given by the formula and its diameter (d) is given by d=2r. arrange the equations in the correct sequence to rewrite the formula for diameter in terms of the area of the circle.

Find the percent error of the measurement 4 cm