Complete each calculation. Express your answer to the correct number of significant digits.

Question

a)4.02mL + 3.76mL +0.95mL
b)(2.7 x 10^2m) x (4.23 x 10^2m)
c)5092kg divided by 23L
d) 2-6.3 + 6-7
e)(6.853 x 10^3L) + (5.40 x 10^3mL)
f)(572.3g + 794.1g) divided (24mL + 52mL)

My answers:
a)8.7mL
b) i am not sure
c) 221.34
d) -5.3
e) im not sure
f) 17.97

Answer 1

a. You are allowed to the hundredths place so the answer should be 8.73.
b. 1.1421E5. In mult and division, you are allowed as many places in the answer as you have the smallest number that has been mult or divided. You have 2 s.f. in 2.7E2 and 3 in 4.23E2 so you are allowed 2 in the answer. So you round 1.1421E5 to 1.1E5.
c. 2.213913E2. From the rule above you are allowed 2 s.f. and the answer is rounded to 2.2E2 kg/L.
d. -5.30. You are allowed only units (no tenths) so round to -5
e. 12.253E3. You are allowed to the hundredths so round to 12.25E3 or 1.225E4
r. 17.9789 Adding the first two numbers is ok to the tenths or 4 s.f. The divisor has 2 s.f. So you're allowed 2 in the answer which should be rounded to 18
I think you need to review s.f. Here is a good site.
http://www.chemteam.info/SigFigs/SigFigs.html

Answer 2

thank you so much, yes the site is helpful