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## anonymous one year ago Can someone please help? The circumference of the Earth is approximately 131,000,000 ft. a. Write this number in scientific notation and tell how you knew whether to use a positive or a negative exponent. b. The circumference of Mars is 7.00 x 107. Which planet is larger, and by how many feet? Write the answer in both standard and scientific notation.

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1. anonymous

In scientific notation there can only be 1 number left of the decimal point. Your decimal point is at the end of the number. How many spots must it move and in what direction to get it behind the first 1?

2. anonymous

6 times

3. anonymous

no, if you move it 6 times there will be 3 digits left of decimal. |dw:1441997504656:dw|

4. anonymous

8 times

5. anonymous

okay

6. anonymous

$1.31 \times 10^{8}$

7. anonymous

do you understand?

8. anonymous

yes I do

9. anonymous

for part b you just have to subtract the numbers

10. anonymous

okay

11. anonymous

-9999993

12. anonymous

subtract the number from b from the number in a $$7 \times 10^7$$ is the same as 70,000,000 so do $$131,000,000-70,000,000$$

13. anonymous

61,000,000

14. anonymous

yeah that's the answer in standard notation. How would you write it in scientific notation?

15. anonymous

fyi this page has notes on converting between standard and scientific notations, as well as an applet that does it for you https://www.mathsisfun.com/numbers/scientific-notation.html

16. anonymous

6.1 x 10^7

17. anonymous

that's right

18. anonymous

okay thank you

19. anonymous

you're welcome

20. anonymous

Goodbye, for now

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