Any Mathematicians Out There

[zingo1327]

I'm sure the answer is simple but my old brain has stopped working. My petrol tank was 25% full. I topped it up to full and it cost me £40. If I had let the tank run empty how much would it cost to fill it up to 100%? I would be grateful if you could explain how you worked it out. thanks in advance

[Buenchico]

Three quarters of a tank cost you £40.

So one quarter of a tank would have cost you a third of that = £13.33.

Add that onto the three quarters, to give you a full tank, and you get £53.33.

[DTCwordfan]

I could say three quarters of what it would cost to by Chelzea FC....

40/.75 is the answer, just over 53 pounds.

[Barmaid]

75% of your tank cost you £40. If you divide 40 by 75, you get the value of 1%. That is 0.53. If you multiply the value of 1% by 100 you get £53.33. That is what it would cost you, roughly to fill up your take from empty.

Although in reality it would cost a lot more. a) because petrol tanks normally have a small reserve and b) if you run out of petrol, you are then going to have the additional cost of getting your car to a fuel supply or a fuel supply to your car.

[Hopkirk]

Caveat:

Your petrol gauge will be very inaccurate for this sort of calculation.
Some people manage to drive considerable distances with the guage showing empty. (Not me. I get fuel anxiety when I get near the red).

[Hopkirk]

How do you spell that fuel measuring device?

[Buenchico]

Incidentally, you've either got a very small petrol tank or you've discovered somewhere with amazingly cheap fuel! Filling a 'typical' 55 litre tank generally costs around £90 these days.

[elliemay1]

I find it easier to divide by 3, then multiply by 4

[THECORBYLOON]

25% full means 75% empty.

75% is the same as 3/4

3/4 tank (T) cost £40 in petrol

3/4 × T = £40
3 × T = 4 × £40
T = 4/3 × £40
T = £53.33

To check that,
£53.33 × 75% = £40

[bednobs]

it is interesting how it can be done in many different ways.
I diveded your £40 by 3 (to get a quarter) and then times it by 4 to get a whole :)

[elliemay1]

^ Me too bednobs!

[Cloverjo]

Buenchico, it costs about £45 to fill up my Mini. Perhaps the OP has a small car too.

[Peter Pedant]

the difference is 75% and it cost £40.00 - say 39 as it is easier
so the difference you NEED is 25 % - 75% + 25% = full

if 75% cost 39 then 25% costs a third - £13 - ( £13.33 to eb exact)
so whack on £13 ( £13.33 to be ezxact)

and you get - - £53 - - or £53.33

[ToraToraTora]

40 / 0.75 = 53.33, simples!

[Peter Pedant]

I did this ten times a day for 30 d - for a neighbours child
and on retesting at skool - - she went up a year !

she was the only one in the class who cd do it and so was called out to show the other thick so and so's

Pts much more grateful than she was

[Peter Pedant]

yeah foo TTT but 'easy' isnt a good way to sum up your working - see OP

[gingejbee]

I'm not sure that a "mathematician" is needed for this calculation...witness the above!

[Ellipsis]

> If I had let the tank run empty how much would it cost to fill it up to 100%?

Depends what the fuel price had risen to since you last filled up!

Assuming the fuel price of the two fills was exactly the same:

(40/3)*4 = £53.33

Assuming the fuel price had risen 20% since your last fill-up:

(40/3)*4*1.2 = £64.00

[Buenchico]

>>> Buenchico, it costs about £45 to fill up my Mini

Nearly all minis have a 40 litre petrol tank. At 163.28p per litre (which is the current UK average price, according to the RAC website). That's about £65 for a full tank when refilling from empty.

The 'average family car', that's so often cited by the media, has a 55 litre tank. That costs about £90 to fill from empty.

[Barmaid]

I put slightly less than 3/4 tank in our car today and it was £90!!!!

[Zacs-Master]

My wife’s mini doesn’t have a 55ltr tank.