I bought this calculator, there is a month and a half for my daughter (just before school starts). She used it 3 times and then only during a math exam bam !!! nothing, it no longer works. We changed the batteries, or anything done !! In short this is because more than 30 days now that we bought and we have not received any invoice worthy of the name with the product, it's for our apple !! I find it shameful !! is theft, I can not even make a claim! Either I got a bad batch or be on a secondhand, but this is the last time I buy on Amazon, because it hurts 65 Euros for my apple Thanks !!