Why can I not do this mental maths in my head and can you tell me how I could?

[LindorDoubleChoc]

I bought a box of dishwasher tablets in Lidl today.

It was £2.50 for 50 tablets.

I cannot work out if they are 50p per tablet or 5p per tablet. I have also put it through a calculator and still don't know!

I do have a maths block, but why is this still a problem for me?

Can anyone make it easy, very very easy, to understand.

They are 5p per tablet. If you added up 50 pence pieces you’d only need five to get to £2.50

convert the £2.50 to pence = 250 The zeroes cancel each other out and then you divide 25 by 5 = 5p. In order for it to be 50p per tablet, there'd only be 5 in the box!

Turn the pounds into pence. Its 250 pence. 5x50. So 5p each.

Does it make it easier if you take the 0 off the end of each number so 25p for 5 tablets ?
(Taking a 0 off each number is dividing each by 10)
25p divided by 5 = 5p

An easy way - 50p x 10 = £5 therefore you know it must be 5p because you have more than 10 tablets. I'm crap at mental arithmetic so I try to find ways to multiply by 10 and then subtract/divide from a round number but in this case it's an easy sense-check.

You know that 2x50p is £1.
So 50x50p cannot be £2.50

Fascinated by all the different thought processes! I thought about it differently - £2.50 for 50 would be £5 for 100 - and hence they’re 5p each.

This is how I did it as well

There are a variety of ways to do it, just use the one you feel more comfortable with.

£2.50 for 50 tablets is the same as £5.00 for 100 tablets and it is far easier to divide something by 100. You move the decimal point 2 places = £0.05 or in other words, 5p.
Alternatively -
£5.00 divided by 10 gives you 50p for 10 tablets.
Divide by 10 again gives you 5p per tablet.

OR - if 50 tablets cost £2.50 then 5 tablets must cost £0.25. If 5 tablets cost 25p then they must be 5p each.

Other ways of doing it are available.

You pretty much had it - you just needed to switch your mind from doing the maths to stepping back and applying common sense. As per other posters, it can’t possibly be 50p if you think about it logically.

50 for £2.50
So you work out how many ten would cost
How many tens in 50? Five and divide the other side by that

5s into £2 50 is fifty pence

10 for 50
1 for 5 (50 divided by 10 or just take your zeroes off)

five pence each

Then check it back
50 @10p would be a fiver so
50 @ five pence would be half that amount!

I get a total blank too, op, when i try to do mental maths especially if I am tired or increasingly, if I'm multi tasking - and I'm really good at maths normally! Don't be too hard on yourself.

Ignore the decimal point so it is 250 pence.

Then work out how many 50's are in 250 which is 5 so it is 5 pence per tablet.

Or double it.

£2.50 for 50
£5 for 100

Then if £5 converted to pence is 500.... It's 500 pence divided by 100.... it's 5p each. Good deal!

Perfect!

I think it’s easier if you think in old fashioned coins. Picture a 50p coin. Now if you add another one you already have a pound. So you only need 5 of the 50p coins to make £2.50.

If you have 5p coins you need 50 of those to make £2.50.

Paying everything by card means that we don’t get a lot of practice for this kind of maths anymore…