# significant figures!?

how many significant figures are in:

2.520 x 10^4 mi/hr=??????? significant figures

0.000627 lb/ft^3=???????? significant figures

0.8 x 10^6 m/sec=??????? significant figures

answer with correct number of significant figures

1.5m+3.34m+162m+10.137m=???????? meters

111m+111dm+111cm+111mm=?????? meters

25.0 mi/hr x 5280 ft/mi x 1 hr/3600 sec=???????? ft/sec

calculate the properly rounded area of a square that is measured to have sides of 7cm= (it's not 49cm)

what is the uncertain digit in each case?

5.00mm

5.00 x 10^-6

5288 ft

2001 in

0.00023 m

i will give 10 points if the person tried

Relevance

how many significant figures are in:

2.520 x 10^4 mi/hr=??????? significant figures

4

Count all non-zero digits + all trailing zeroes which fall AFTER a decimal or are FOLLOWED by a decimal.

0.000627 lb/ft^3=???????? significant figures

3

Count all non-zero digits

0.8 x 10^6 m/sec=??????? significant figures

1

answer with correct number of significant figures

1.5m + 3.34m + 162m + 10.137m = ???????? meters

176.977 too many sig figs

177 m

Since 162 m has its last sig fig in the ones place, your answer is only accurate to the ones place.

Add everything, as written, then round to the correct sig figs

111m + 111dm + 111cm + 111mm = ?????? meters

Convert everything to the same measure, let's use m.

111 m + 11.1 m + 1.11 m + .111 m =

123.321 m

Again, we have to look at accuracy level involved and go with the least accurate figure, which is 111 m. It ends in the ones column, so the answer must also end in the ones column.

123 m

25.0 mi/hr x 5280 ft/mi x 1 hr/3600 sec=???????? ft/sec

25.0 has 3 sig figs

5280 has 3 sig figs (0 doesn't count because it is not followed by a decimal point)

3600 has 2 sig figs (0's don't count because they are not followed by a decimal)

36.6666666666.....

Answer may only contain 2 sig figs, because 3600 only has 2 sig figs.

37 ft/sec

calculate the properly rounded area of a square that is measured to have sides of 7cm= (it's not 49cm)

7 has only 1 sig fig, so the answer may contain only 1 sig fig

Round 49 to one sig fig gives:

50 cm^2 (since there is no decimal following the 0, the 0 does not count)

what is the uncertain digit in each case?

5.00 mm

The final 0. Hundredths place.

5.00 x 10^-6

The final 0. Hundredths place.

5288 ft

The second 8. Ones place.

2001 in

The 1. Ones place.

0.00023 m

The 3. Hundred-thousandths place.

5000

Has 1 sig fig

5.0 x 10^3

Has 2 sig figs

5.00 x 10^3

Has 3 sig figs

5.000 x 10^3

Has 4 sig figs

5000.

Has 4 sig figs

5280

Has 3 sig figs

5.280 x 10^3

Has 4 sig figs

Notice how the decimal placement affects the number of significant figures. It is awkward to write a number such as 5000. to indicate 4 sig figs, which is why you would normally see this written as 5.000 x 10^3, instead.

Zeroes are probably the most difficult concept to learn when learning about significant figures. I found a really easy to follow tutorial on significant figures you might want to take a look at. It explains sig figs really well, including zeroes and exact numbers. The same site has tutorials on uncertainty in measurement and sig figs and rounding.

http://www.chem.sc.edu/faculty/morgan/resources/si...