Step-by-step explanation:
Sn=n/2(2a+(n-1)d)
910=n/2{2a+(n-1)d}
1820=n{2a+(n-1)d}
1820=20{2a+(20-1)d}
1820=20{2a+19d}
91=2a+19d
An=a+(n-1)d
95=a+(20-1)d
95=a+19d
91=2a+19d
---------------
4=-a
a=-4
91=2a+19d
91=2(-4)+19d
91=-8+19d
91+8=19d
99=19d
d=99/19
A=-4
Answer:
X= -15/7
Step-by-step explanation:
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Answer:
D. 165
Step-by-step explanation:
if A+n=180
75+90+n=180
165+n=180
n=180-165
n=15
A+n=180
A+15=180
A=180-15
A=165 (D)
The z-score of the information given is:
z=(x-μ)/σ
where
μ-mean
σ- standard deviation
from the information given:
x=93.02
μ=89
σ=√625=25
hence
z=(93.02-89)/25
z=0.1608
thus
P(X≥x)=1-0.5636=0.4364=43.64%
