Hopping mad atm. And concerned.

DC4 (Y11) proudly showed me her maths mock papers. Grade A overall

but... Question 1 on the non-calc. paper was 1.87 x 48 (or similar) and she got it wrong - worse still, she appeared to have no idea how to work it out! Says she didn't know where the decimal points went!

Same child got A*A*A in the three sciences in Y10 - generally capable of the basics in maths - or so I thought! And I'm pretty sure, if memory is correct, she could multiply decimals 6 years ago for her 11 plus exam.

She seemed not to know which method to use. I tried to butt in with helpful advice but got told off before I had even uttered a complete sentence.

Not entirely sure what (half) came out of my mouth would have constituted a grammatically correct sentence anyway. Looking through the paper it didn't seem to be a one off either.

What concerns me is that such simple maths I thought was ingrained - i.e. so well known one just couldn't forget how to do it. Obviously not.

How can a bright Y11 child just forget how to do this?

I just don't get how she could forget.

(no, if you're wondering, she has not picked maths as an A level)