The formula that can be used to obtain a convergent series is given by; 
 a/1 – r.
<h3>What is a series?</h3>
In mathematics, we define a series as sum of numbers which could be convergent or divergent. In a convergent series, the summation of the numbers approaches a given value.
The formula that can be used to obtain a convergent series is given by; 
 a/1 – r.
Learn more about a convergent series:brainly.com/question/15415793?
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Answer:
option (c) is correct 
Explanation:
Half life of a substance is the time in which the element becomes half of is initial value.
half life, T = 8 days 
Amount remaining, N = 10 % of original value 
Let the original value is No. 
N = 10% of No
N = 0.1 No
Let the time taken is t and the decay constant is λ.
The relation between the decay constant and the half life is given by 

Us the equation of radioactivity 



Taking natural log on both the sides, we get 
0.08664 t = 2.303
t = 26.6 days
 
        
             
        
        
        
Answer:
8000J
Explanation:
The kinetic energy of the car lost during breaking are converted to thermal energy and are gained by the brakes.
Kinetic energy loss by car = thermal energy gained by brakes.
∆K.E = ∆T.E ....1
The Kinetic energy loss by car can be expressed as;
∆K.E = K.E1 - K.E2
Initial K.E = K.E1 = 10000J
Final K.E = K.E2 = 2000J
∆K.E= 10000J - 2000J = 8000J
From equation 1, 
∆K.E = ∆T.E 
∆T.E = 8,000J
thermal energy gain by brakes = 8,000J
 
        
             
        
        
        
A speed does not involve the element of direction.
        
             
        
        
        
Answer: Non metal.
Explanation: Carbon has 4 electrons in it’s valence shell which makes it a metalloid but commonly it is considered as a non metal.