A5 / a1 = r^4 = 324/4
So r^4 = 81
r = +/- 3
If r = 3 :-
S5 = 4 * (3^5-1) / (3-1) = 484
so r = 3 Answer
Answer:
It is pi/2
Step-by-step explanation:
Answer:
Incomplete question
This is the complete question
A stone falls from the top of a cliff into the ocean.
In the air, it had an average speed of 16 m/s. In the water, it had an average speed of 3 m/s before hitting the seabed. The total distance from the top of the cliff to the seabed is 127 meters, and the stone's entire fall took 12 seconds.
How long did the stone fall in air and how long did it fall in the water?
Step-by-step explanation:
The stone speed in air Sa =16m/s
The stone speed in water Sw=3m/s
Total distance travelled is 127m
Total time taken is 12 sec
Let time in air be ta
Tune in water be tw
Therefore
Total time =ta +tw
12=ta+tw. ,Equation 1
ta=12-tw. ,Equation 2
Also
Speed is given as
Speed = distance /time
Distance =speed × time
So, total distance = distance traveled in air + distance travelled in water
127= Sa×ta + Sw×tw
127=16ta+3tw. , Equation 3
Substitute equation 2 into. 3
127=16(12-tw)+3tw
127=192-16tw+3tw
127-192=-13tw
-65=-13tw
tw=-65/-13
tw=5 seconds
Also from equation 2
ta=12-tw
ta=12-5
ta=7 seconds
The stone spent 7 seconds in air and spent 5 seconds in water before getting to the seabeds
Answer:
The reason why standard deviation of the entire class is greater than standard deviation of males and females considered separately, is that mean values for males and females are different from each other.
Step-by-step explanation:
The concept of mean is well represented by the following formula
mean = , where x1, x2, xn are the observations and N is the number of observations (population).
Standard deviation represents the distance between each observation and the mean of the population (all observations). The formula for this parameter is:
Standard deviation =√[((x1 - x)² + (x2-x)² + ....+ (xn-x)²)/N-1], where x1, x2,..., xn are the observations and x is the mean value.
In this case you have that each height registered is an observation and the number of observations represents the N value. As you can see if the mean for males is different from that of females their standard deviation will be different too. Usually males have heigths greater than that of females (1.77 vs 1.64, in USA for example), and heights inside each group will be more similar than between groups. Then, when you mix all observation there will be an increase in standard deviation, because you are mixing very different heigths