Question

C. Round off each of the following
quantities to three significant figures :
a. 1.43 cm b. 458 x 102 cm
c. 643 cm² d. 0.039 m
e. 6.398 10-3 km
f. 0.0179 g g. 79,000 m
h. 42,150 i. 649.85;
j. 23,642,000 mm
k. 0.0041962 kg​

Answer 1

Answer:

Significant figures : The figures in a number which express the value -the magnitude of a quantity to a specific degree of accuracy is known as significant digits.

Rules for significant figures:

Digits from 1 to 9 are always significant and have infinite number of significant figures.

All non-zero numbers are always significant.

All zero’s between integers are always significant.

All zero’s preceding the first integers are never significant.

All zero’s after the decimal point are always significant.

1. 1.43 cm has three significant figures.

2. $458\times 10^2$ can be written as $4.58\times 10^4$ in  three significant figures.

3. 643 can be written as $6.43\times 10^2$ in  three significant figures.

4. 0.039 m can be written as $3.90\times 10^{-2}$ in  three significant figures.

5. $6.398\times 10^{-3}km$ can be written as $6.40\times 10^2$ in  three significant figures.

6. 0.0179 g can be written as $1.79\times 10^{-2}$ in  three significant figures.

7. 79,000 m can be written as $7.90\times 10^3$ in  three significant figures.

8. 42,150 can be written as $4.22\times 10^4$ in  three significant figures.

9. 649.85 can be written as $650$ in three significant figures.

10. 23,642,000 mm  can be written as  $2.36\times 10^7$  in  three significant figures.

11. 0.0041962 kg​ can be written as  $4.20\times 10^{-3}$ in three significant figures.