Answer:
a) the common difference is 20
b) 
c) the common difference is -13
d) 
Step-by-step explanation:
a) what is the common difference of the sequence xn
Looking at the table, we get x_3=16, x_4=36 and x_5= 56
Deterring the common difference by subtracting x_4 from x_3 we get
36-16 =20
So, the common difference is 20
b) what is x_8? what is x_12
The formula used is: 
We know common difference d= 20, we need to find 
Using
we can find 

So, We have 
Now finding 

So, 
Now finding 

So, 
c) what is the common difference of the sequence 
Looking at the table, we get a_7=104, a_8=91 and a_9= 78
Deterring the common difference by subtracting a_7 from a_8 we get
91-104 =-13
So, the common difference is -13
d) what is a_12? what is a_15?
The formula used is: 
We know common difference d= -13, we need to find 
Using
we can find 

So, We have 
Now finding
, put n=12

So, 
Now finding
, put n=15

So, 
The answer is 15.525. All you have to do is divide 279.45 by 18 which gives you 15.525.
Answer:
<h2>C. <em>
20,160</em></h2>
Step-by-step explanation:
This question bothers on permutation since we are to select a some people out of a group of people and then arrange in a straight line. If r object are to be arranged in a straight line when selecting them from n pool of objects. This can be done in nPr number of ways.
nPr = n!/(n-r)!
Selection of 6 people out of 8 people can therefore be done in 8C6 number of ways.
8P6 = 8!/(8-6)!
8P6 = 8!/2!
8P6 = 8*7*6*5*4*3*2!/2!
8P6 = 8*7*6*5*4*3
8P6 = 56*360
8P6 = 20,160
<em>Hence this can be done in 20,160 number of ways</em>
Answer:
49 seconds
Step-by-step explanation:
The time perry used is 7/8 of a minute
a minute equals to 60 seconds
so the time perry used is 7/8 x 60 = 52.5 seconds
The winner used 14/15 of 52.5 seconds (perrys time)
so 14/15 x 52.5 = 49 seconds