how many significant figures are in the following:

4001.006
0.0000456
10001.00000
10.000000456
2000000
2000000.0
20000000000.00
20

Here is a good site for s.f.

http://members.aol.com/profchm/sig_fig.html

can u just help me with liek two?

its hard

4001.006

0.0000456

s.f. = significant figure or significant digit.
Zeros between digits count as s.f. and digits are s.f.; therefore, this number has 7 s.f.
The second one is a different kind. Leading zeros don't count as s.f.; therefore, this one has only 3 s.f.
Read that site I give you. It explains s.f. VERY WELL. And it isn't hard but you must follow the rules.

To determine the number of significant figures in a given number, you need to follow these guidelines:

1. Non-zero digits are always significant. For example, "4" in 4001.006, and "2" in 2000000.

2. Any non-zero digit sandwiched between two significant figures is also considered significant. For example, "1" in 4001.006, and "1" in 10001.00000.

3. Zeros that are not between significant figures are not significant. For example, "0" in 4001.006 before the decimal point, and "0" in 2000000 after the significant figures.

4. Leading zeros (zeros before any non-zero digit) are NOT significant. For example, "0" in 0.0000456.

5. Trailing zeros (zeros after the last non-zero digit) are significant only if there is a decimal point in the number. For example, "00" in 20000000000.00.

Now let's apply these rules to the given numbers:

1. 4001.006 - This number has 7 significant figures.

2. 0.0000456 - This number has 3 significant figures.

3. 10001.00000 - This number has 6 significant figures.

4. 10.000000456 - This number has 12 significant figures.

5. 2000000 - This number has 1 significant figure.

6. 2000000.0 - This number has 8 significant figures.

7. 20000000000.00 - This number has 11 significant figures.

8. 20 - This number has 1 significant figure.