Find the 84th percentile, P84, from the following data 1 2 4 6 18
22 23 30 32 33
40 44 46 48 49
50 55 56 61 63
71 72 74 77 78
80 81 87 95 100

80.04

Step-by-step explanation:

It is already arranged in ascending order,

N=30

P84=i((N+1)/100)=84(31/100)=26.04 th item

26.04th item=(26+(27-26(0.04))) th item

80+81-80(0.04)=80+0.04=80.04

hello from mrbilldoesmath!

answer:

a(n) - a(n-1) -3

discussion:

this ones a bit interesting. given a(n) = 5 - 3n consider this:

a(n-1) = 5 - 3(n-1)

          = (5 - 3n) + 3             => but a(n) = 5 - 3n, the first term

          = a(n)   + 3                 => subtract 3 from both sides

a(n-1) -3 = a(n)  

or

a(n) - a(n-1) -3

you,

mrb