An element makes up 0.0021% of the Earth's continental crust by mass. Express this in ppm (parts per million), to an appropriate number of significant figures

How many significant figures are there in (a) 78.9 ± 0.2, (b) 3.788 × 10

(a) How many significant figures are in the numbers 999.0 and 1000.0? 999.01000.0 (b) If the uncertainty in each number is 10, what is the percent uncertainty in each? (Give your answer to 4 significant figures.) 999.0  %1000.0  % (c) Which is a more meaningful way to express the accuracy of these two numbers, significant figures or percent uncertainties?

3.

A partly-full paint can has 0.499 U.S. gallons of paint left in it. (a) What is the volume of the paint, in cubic meters? (b) If all the remaining paint is used to coat a wall evenly (wall area = 14.6 m²), how thick is the layer of wet paint? Give your answer in meters. (a) Number i (b) Number i Units Units + -

How many significant figures are there in (a) 0.0210, (b) 5.060, (c) 7.10 * 10-4,(d) 1.0 * 105?

- Your answer is partially correct. A partly-full paint can has 0.515 U.S. gallons of paint left in it. (a) What is the volume of the paint, in cubic meters? (b) If all the remaining paint is used to coat a wall evenly (wall area = 12.1 m²), how thick is the layer of wet paint? Give your answer in meters. (a) Number i 1.949 (b) Number i 312.1 Units Units m^3 m^2

A study fonds that the metabolic rate of mamals is proportional to the mass of the mamal carried to the exponent of (3/4). By what factor does the metabolic rate of a 70.0 kg human exceed that of a 6.30 kg cat?\ 70.0 3/4 kg    = 6.09 6.303/4 kg I set up the values as a ratio and came up with 6.09. OK, I answered my own question. That is the correct answer.

Still think that unit conversion isn't important? Here is a widely publicized, true story about how failing to convert units resulted in a huge loss. In 1998, the Mars Climate Orbiter probe crashed into the surface of Mars, instead of entering orbit. The resulting inguiry revealed that NASA navigators had been making minor course corrections in SI units, whereas the software written by the probe's makers implicitly used British units. In the United States, most scientists use Sl units, whereas most engineers use the British, or Imperial, system of units. (Interestingly, British units are not used in Britain.) For these two groups to be able to communicate to one another, unit conversions are necessary. The unit of force in the SI system is the newton (N), which is defined in terms of basic Sl units as 1 N=1 kg · m/s?. The unit of force in the British system is the pound (lb), which is defined in terms of the slug (British unit of mass), foot (ft), and second (s) as 1 lb =1 slug ·…

the average density of an atom is approximately 103 kg/m3. The nucleus of an atom has a radius about 10-5 times that of the entire atom, and contains nearly all the mass of the atom.  What is the approximate density, in kilograms per cubic meter, of a nucleus?