I think I did the Chem P2 variant 2. I liked the organic chem + kinetic theory in it but not so much the oxidation numbers part, though I was lucky to have remembered the exception for metal hydrides.
Does anyone know the correct answer for the permutations Q in maths P6? It was the one that asked for for the different 3 digit and 4 digit numbers able to be produced from the numbers 1,3,5,6 and the digits formed had to be >500 as well as being odd numbers. So far I've heard varying answers
thanks
Just so you know, the correct answer is 28. The way to calculate is as follows :
a) 3-digit cases
i) Beginning with 5,
5 _ _ --> The last blank will let you have 2 possibilities (1 and 3) and after putting 1 number the 2nd blank will have 2 possibilities (1 and 6 or 3 and 6 depending on your last digit) = 2 x 2 = 4
ii) Beginning with 6,
6 _ _ --> Last blank 3 possibilities (1,3 or 5) and after 1 number, 2nd blank will have 2 possibilities as 2 numbers left = 2 x 3 = 6
b) 4-digit case
_ _ _ _ --> The last blank must be an odd number (1,3 or 5), the other blanks can be arranged by any order = 3! x 3 (for the last blank) = 18
Total = 4 + 6 + 18 = 28
There's your answer! I forgot to consider odd digits for the 4-digit case ~_~ Careless me.
