What is 58,000,000,000 estimated as the product of a single digit and a power of 10?

a. 5 x 10^9
b. 5 x 10^10
c. 6 x 10^9
d. 6 x 10^10

The number 58,000,000 is number that may be expressed in its scientific notation as  5.8 x 10^9. However, we are asked to answer such that the product be of single digit only. That is obtained by rounding the number 5.8 to 6. Thus, the answer is 6 x 10^9. 

It’s 24.6 after you round to the nearest tenths the answer should be 25.0