math

Please check my math answers (and correct?)?

I have some math questions, please check them, (they are multi choice, check if my answer is correct. if not, please say which is correct)

1. What is the simplified form of the expression –(10)–1?
a -1/10
b -1/-1^10 (my answer)
c 1/10
d 10

2. Suppose that the amount of algae in a pond doubles every 4 hours. If the pond initially contains 90 pounds of algae, how much algae will be in the pond after 12 hours?
720 pounds
360 pounds
1,440 pounds (my answer)
114 pounds

For questions 3–4, determine if the number is written in scientific notation. If not, explain.

3. 4.8 × 1007
No; it is not written as a number times a power of 10.
Yes; the number is written in scientific notation.
No; the first factor is not a number between 1 and 10. (my answer)

4. 5.1 × 10–8
Yes; the number is written in scientific notation.
No; the first factor is not a number between 1 and 10. (my answer)
No; it is not written as a number times a power of 10.

5. Suppose that the volumes of four stars in the Milky Way are 2.7 × 1018 km3, 6.9 × 1012 km3, 2.2 × 1012 km3, and 4.9 × 1021 km3. What is the order of the stars from least to greatest volume?

2.7 × 1018 km3, 6.9 × 1012 km3, 4.9 × 1021 km3, 2.2 × 1012 km3
2.2 × 1012 km3, 6.9 × 1012 km3, 2.7 × 1018 km3, 4.9 × 1021 km3
2.7 × 1018 km3,6.9 × 1012 km3, 2.2 × 1012 km3, 4.9 × 1021 km3
2.2 × 1012 km3, 4.9 × 1021 km3, 2.7 × 1018 km3, 6.9 × 1012 km3 (my answer)

6. Suppose that the diameters of different types of hairs are 1.7 × 10–4 cm, 1.4 × 10–3 cm, 1.2 × 10–5 cm, and 1.9 × 10–4 cm. What is the order of the hairs from least to greatest diameters?

1.9 × 10–4 cm, 1.7 × 10–4 cm, 1.4 × 10–3 cm, 1.2 × 10–5 cm
1.2 × 10–5 cm, 1.7 × 10–4 cm, 1.9 × 10–4 cm, 1.4 × 10–3 cm (my answer)
1.9 × 10–4 cm, 1.7 × 10–4 cm, 1.2 × 10–5 cm, 1.4 × 10–3 cm
1.2 × 10–5 cm,1.4 × 10–3 cm, 1.9 × 10–4 cm, 1.7 × 10–4 cm

7. What is the order of 1.5 × 103, 1.4 × 10–1, 2 × 103, and 1.4 × 10–2 from least to greatest?
1.4 × 10–2, 1.4 × 10–1, 1.5 × 103, 2 × 103
1.4 × 10–1, 1.4 × 10–2, 2 × 103, 1.5 × 103 (my answer)
2 × 103, 1.5 × 103, 1.4 × 10–1, 1.4 × 10–2
2 × 103, 1.4 × 10–2, 1.5 × 103, 1.4 × 10–1

8. Simplify this expression. (–4)–6(–4)7

413
–4 (my answer)
13
1

For questions 9–10, find the simplified form of the expression. Give your answer in scientific notation.

9. (8 × 107)(7 × 104)
1.5 × 1012
5.6 × 1012
1.5 × 1029 (my answer)
5.6 × 1,029

10. (3 × 106)(8 × 10–4)
1.1 × 103
2.4 × 103
1.1 × 10–23 (my answer)
2.4 × 10–23

11. Astronomers measure large distances in light-years. One light-year is the distance that light can travel in one year, or approximately 5.88 × 1012 miles. Suppose a star is 9.8 × 101 light-years from Earth. In scientific notation, approximately how many miles is it?
5.88 × 1013 miles
5.76 × 1014 miles (my answer)
5.88 × 1012 miles
9.8 × 1012 miles

12. What is the simplified form of the expression? (y–5)–10y10
y–60
y60
y–150 (my answer)

13. Radio signals travel at a rate 3 × 108 of meters per second. How many seconds would it take for a radio signal to travel from a satellite to the surface of the Earth if the satellite is orbiting at a height of 3.6 × 107 meters?
8.3 seconds
1.2 × 10–1 seconds (my answer)
1.08 × 1016 seconds
10.8 × 1015 seconds

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17. Does the rule y = –3x5 represent an exponential function?
yes (my answer)
no

For questions 23–24, find the balance in the account.

23. $3,300 principal earning 4%, compounded annually, after 3 years
$3,712.05
$211,200.00
$3,696.00
$10,296.00 (my answer)

24. $1,600 principal earning 7%, compounded semi-annually, after 33 years
$4,979.11
$14,920.54 (my answer)
$112,992.00
$15,494.70

25. A tractor costs $15,450 and depreciates in value by 14% per year. How much will the tractor be worth after 3 years?
$22,889.85
$15,408.00
$8,451.28 (my answer)
$9,827.07

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  1. 1.
    -10 * -1 = 10

    2.
    doubles to * 2 at 4
    doubles to * 4 at 8
    doubles to * 8 at 12
    8*90 = 720

    3. No because not a power of ten. Your answer is wrong
    4.8 IS between one and ten
    1007 is NOT a power of ten. Perhaps 10^7 ????

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  2. 4.
    It would be correct if you typed it correctly
    5.1 * 10^-8
    Your answer is nonsense.

    the ^ symbol means "to the power" or superscript

    5. Nonsense again
    10^12 (Please learn to type exponents) is smaller than ANYTHING * 10^13 or 14 or 21 or whatever bigger than 12

    Enough already. You are just giving random answers and asking me to do them

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  3. dang damon why u so pressed? get over urself ur not a big shot guy

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  4. thanks so much everyone!! :DD

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  5. last question i hope is correct lol

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