1. ### Perms and Coms question

Hi I need help with a question from the Cambridge 2u textbook (EX1C 13) A piece of paper 0.01mm thick is folded successively 100 times. How thick is it now? Most of the questions were alright but this one really stumped me. Any help would be great.

3. ### Quick Maths Q.

Hello, hello! I'll cut right to it. I'm confused why the answer is 16 - and feel especially stupid because you get that from 249 - 233, however i don't see the connection. Can someone explain this to me? The sum of 50 terms of an arithmetic series is 249 and the sum of 49 terms of the...
4. ### Need 3D trig question help

The diagram shows a rectangular pyramid. X and Y are the midpoints of AD and BC respectively and T is directly above Z. TX = 15cm, TY = 20cm, AB = 25cm and BC = 10cm. a) Show that ∠XTY = 90°. b) Using Pythagoras’ theorem, show that TZ = 12 cm.
5. ### basic trig question

Hi Guys, In the screenshot I've attached (from my textbook), how is that 100 degree angle as well as that -40, 320 degree angle possible? I would have thought they would be around 350 and 100 respectively? Sorry if I'm missing something really obvious