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If three primes are randomly selected from the prime numbers
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26 Apr 2020, 12:26
26 Apr 2020, 12:26
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44% (02:08) correct
55% (02:40) wrong based on 52 sessions
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If three primes are randomly selected from the prime numbers less than 30 and no prime can be chosen more than once, what is the probability that the sum of the three prime numbers selected will be even?
A. 10%
B. 27%
C. 30%
D. 36.5%
E. 42%
A. 10%
B. 27%
C. 30%
D. 36.5%
E. 42%
Re: If three primes are randomly selected from the prime numbers
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26 Apr 2020, 14:47
26 Apr 2020, 14:47
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Expert Reply
Only one prime number is even and all other primes are odd. So for the sum to be even : two primes should be odd and the other one should be even prime.
No. of prime number (2,3,5,7,11,13,17,19, 23, 29) = 10 numbers.
Even prime can be selected in 1C1 ways = 1
Odd prime can be selected in 9C2 ways = 36
Total ways in which 3 numbers can be selected = 10C3 = 120
Therefore percentage of sum of 3 primes being even = (1*36)/120 = (3/10)*100 = 30%
OA - C.
No. of prime number (2,3,5,7,11,13,17,19, 23, 29) = 10 numbers.
Even prime can be selected in 1C1 ways = 1
Odd prime can be selected in 9C2 ways = 36
Total ways in which 3 numbers can be selected = 10C3 = 120
Therefore percentage of sum of 3 primes being even = (1*36)/120 = (3/10)*100 = 30%
OA - C.
Re: If three primes are randomly selected from the prime numbers
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15 Mar 2025, 22:28
15 Mar 2025, 22:28
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