Pleeaseee help me out here with an explanation please

Select the correct answer. joshua likes to read. he read 6 books when he was 6 years old. every year he doubled the number of books he read the previous year. how many total books did he read between the ages of 6 and 10? a. 60 b. 90 c.186 d.187

Need this asap if anyone can i would be very grateful. if you could show workings that would really

The size of a certain cell is 2.5*10^-9m. another cell is 1.5*10^3 times larger. how large is the larger cell in scientific notation?