I've just been studying the maths questions in my psycometric test books. So long division, percentages, ratios, basic trigonometry. This is inline with the practice questions you get on on flight school websites.
So I imagine the maths you learn on the ATPL course will be along those lines and if you find it tough, help will be on hand.
But the main thing is to learn the maths subjects I mentioned above for your selection tests.
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