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# Easy question on significant figures?

How many significant figures do the following problems have?

1. 100

2. 1020 + 23

3. 100.56 - 38

4. -6.138 x 10^3

### 3 Answers

- 1 decade agoFavorite Answer
Here are my notes on significant figures from class.

1.) all nonzero digits are significant (#1-9). Examples: 4 has 1, 55 has 2, 789 has 3, 343297 has 6.

2.) all zeros between nonzero digits are significant. Examples: 4008 has 4, 50.97 has 4, and 408 has 3.

3.) zeros to the right of nonzero digits, but to the left of an "understood" decimal point are NOT significant. Examples: 600 has 1, and 750500 has 4.

4.) If you place the decimal point in, the zero becomes significant. Example 10 is now a range from 1-20 and 10. is a range from 9-11.

5.) In #'s less than 1, zeros to the right of the decimal point that are to the left of the 1st nonzero digit are NEVER significant. Examples: 0.0047 has 2, 0.0007 has 1, 0.06 has 1 and 14.0007 has 6.

6.) In numbers left than 1, the "0" placed to the left of decimal poinn, does NOT count. Example: 0.0007, the zero before the decimal does not count so it could be .0007.

7.) All zeros to the right of a decimal point to the right of a nonzero digit are significant. Examples: 8.0 has 2, 16.40 has 4, 35.000 has 5, 1.50 has 3 and .90 has 2

To answer your questions:

#1 has 1 sig. figure (read rule #3 for explanation)

#2 has 4 sig. figures (answer is 1043, read rule #2)

#3 has 4 sig. figures (answer 62.56, read rule #1, decimal point doesn't matter in this case!)

#4 has 4 sig. figures too (answer is -6138 which has 4, negatives do not matter for sig. figs. (rule #1))

Source(s): just learn for physical science! i have a test on monday! - zsm28Lv 51 decade ago
1. 100 has 3 significant figures

2. 1020 + 23 = 1043 has 4 significant figures

3. 100.56 - 38 has 2 significant figures (because 38 only has 2 significant figures)

4. -6.138 x 10^3 has 4 significant figures

- steenrodLv 44 years ago
you nonetheless ought to round, with sig figs. 2.997 to three sig figs is actual 3.00. for 5 it may well be 2.9979 and for 7 it may well be 2.997924 (if the subsequent huge type is 5, then make the previous huge type even. because that is 4, keep it at 4)