I know that fewer is for countable and less is for uncountable items. However there some exceptions

* Money - I have less than $50 in my wallet
* Distance - I walked fewer than 5 miles this morning

What about measurements - Would it be - I filled up my far with less than 10 gallons of gas this morning or I filled up with fewer than 10 gallons of gas this morning.

Thanks,

'Money' is uncountable by definition.
You can count: dollars, euros, yens, pounds, rupees, yuans, rubles, sheqalims, leva, lei, reals, pesos, nuevos soles, liras and etc. but money is still uncountable :wink:

'Distance' is countable. Example 'compare the two distances...', 'which of the two distances is greater...'
In your example for distance you point 'miles' which is countable and it is OK to use it with fewer.

in general, when you cite a quantity with numbers and units, then you use the words that correspond to uncountable quantities.

the linguistic idea behind this convention is that, when you use numbers and units to describe a quantity, you're measuring something that is, ipso facto, continuous and therefore uncountable. so, if i say 'less than ten gallons of gas', i'm imagining 10 gallons of gas as one large aggregate, and mentioning an aggregate quantity that is less than that 10-gallon aggregate. if i say 'fewer than ten gallons of gas', on the other hand, i'm thinking of buying literal gallons of gas, one at a time, most likely in separate little one-gallon containers.

because distance, like all other quantities measured with scientific units, is also continuous and uncountable, you'd follow the same convention: i walked less than 5 miles this morning.

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if you're scientifically minded enough, here's a different standard you can follow fairly reliably:
if you can feasibly have a decimal quantity of something, then you should use the uncountable forms. if you can't, then use the countable forms.
examples:
less than 5 miles, because it's possible to have something like 4.357 miles
fewer than 5 girls, because it's not possible to have something like 4.357 girls

if you're scientifically minded enough, here's a different standard you can follow fairly reliably:
if you can feasibly have a decimal quantity of something, then you should use the uncountable forms. if you can't, then use the countable forms.

I was doing some Questions from princeton review where it had less than thirty thousand dollars in the original sentence. I corrected it to fewer as I thought I can count it. I was not satisfied with the explanation PR offered saying that the one should use less he/she is refering to the total amount and dont know the actual number. Your explanation seems more clear.

Does the above solution you offered holds good for all appearances of fewer/less (or) any expections?[/i]

I'll answer for Ron - I wouldn't go on record about any grammar rule that it holds true for every possible circumstance and there are no exceptions. English is a mishmash with roots in a bunch of languages - there are exceptions to almost everything. :)

You can generally hold this rule to be true for the vast majority of circumstances however - good enough for this test.