Alan

6t > t + 6

Subtract t from both sides

5t > 6

Divide both sides by 5

t > 6/5   (or t > 1.2 if you prefer)

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You did get it right so I gave you points for it!

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Write 10.3 as (10 + 0.3) then use the binomial expansion on (10 + 0.3)^3 to get:

10^3 + 3*10^2*0.3 + 3*10*0.3^2 + 0.3^3 or

1000 + 90 + 2.7 + 0.027 → 1092.727

Therefore the greatest integer less than 10.3^3 is 1092

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Correct method HeatherF, though something went slightly awry in your calculation of 72/360, which is exactly 0.2, not 0.20571428571 !!

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pH is defined as -log₁₀(hydrogen ion concentration).

True, but what I meant was that you had supplied all the necessary formulas, so it's just a matter of substituting the numbers into them (though I suppose you have to know how to get the molar mass of H₂O from the individual masses supplied)

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Note that, because the diameter is given with units of cm, Headingnorth's result has units of cm²

You've essentially given the solution in your question EinsteinJr!  All you have to do is crunch the numbers (or am I missing something?).

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Very neat shortcut civonamzuk!  I like elegant solutions but I didn't spot this one.

(Actually, it didn't take me very long to produce my results.  I wrote a very short computer program to do it, and let the computer do the work!).

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Some of my  answers are slightly inaccurate.  I rounded down all the "seconds" numbers, whereas I should have rounded them to the nearest second.  

Look at the time between 7 and 8 am for example.  Rounding your result to the nearest second gives 11 seconds, whereas I put 10 seconds.

I doubt if you could tell the difference when actually looking at the clock though!!

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