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May Allah bless u with good grades...b (i) For getting a even number u need the number to end with even number (ofc) well in that number we have 2 4 6 8 as even,
now we consider each separtely
with 2 as end
we have 1 44 687
we rearrange 6! / 2! (we permutate 6 and we need to divide with 2 cuz there are 2 4s)
with 6 and 8 as end it is same thing as with 2
so we get 6!/2! and 6!/2!
with 4 as end we wont have 2 4s, so it will be only 6!
now add
6! + (6!/2!)*3 = 1800
i will try to solve rest soon In Sha Allah
b (ii) to get a number between 20 000 and 30 000 we have to start with number 2 and only, (we cant have a number smaller than 30000 starting with 3 ryt!)
so basically we have 2 and 4 blank
2_ _ _ _
so we permutate 4 from the left 5 numbers
we get 5P4 = 120!
(c) wat a tricky one!
anyway,
see, now since all have same prob, u get that each prob is 1/3
so we start any color and then take any of the other two in next shot
I am not sure if u got my point,
so we 1 * (2/3 )^7
first try is one, becuz all is possible..and power is 7 since 8 - 1 = 7