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Calculate the average of the first 10 prime numbers.
12.5
12.9
13.2
14.1
12.9
Sum the numbers in pairs (e.g., 2+29, 3+23, 5+19, 7+17, 11+13) to quickly reach 129, then divide by 10 by moving the decimal point one place to the left.
The first 10 prime numbers are needed to calculate their average.
Average=nтИСi=1nтАЛxiтАЛтАЛ
Sum the numbers in pairs (e.g., 2+29, 3+23, 5+19, 7+17, 11+13) to quickly reach 129, then divide by 10 by moving the decimal point one place to the left.
Many students incorrectly include 1 as a prime number, which shifts the sum and the average, leading to an incorrect result.
Identify the first 10 prime numbers
List the first 10 prime numbers starting from the smallest prime (2): 2, 3, 5, 7, 11, 13, 17, 19, 23, 29.
P={2,3,5,7,11,13,17,19,23,29}
Calculate the sum
Add the identified prime numbers: 2+3+5+7+11+13+17+19+23+29=129.
тИС=129
Calculate the average
Divide the total sum by the count of numbers (n=10): 129/10=12.9.
Average=10129тАЛ=12.9
B is correct because the sum of the first 10 prime numbers is 129, and dividing this by 10 results in an average of 12.9.
Always verify prime series up to 30; questions regarding the sum of primes are common in competitive exams and are best solved by quick mental grouping to avoid calculation errors.
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