alleryStart learning →Which of these is the complete list of prime numbers less than 20?
A2, 3, 5, 7, 9, 11, 13, 17
B2, 3, 5, 7, 11, 13, 17, 19
C1, 3, 5, 7, 11, 13, 17, 19
D3, 5, 7, 11, 13, 17, 19, 21
Answer & Solution
Correct answer: B. 2, 3, 5, 7, 11, 13, 17, 19
1. A prime number less than 20 must have only 1 and itself as factors.
2. Checking each counting number below 20 against that rule gives 2, 3, 5, 7, 11, 13, 17, and 19.
3. The number 9 fails, since 3 is also a factor of 9, and 1 fails since primes must be greater than 1.
_Source: OpenStax Elementary Algebra (CC BY 4.0), Ch 1 "Foundations", section 1.1 Introduction to Whole Numbers_
Keep practising Foundations
Browse all Foundations questions for CAASPP Mathematics, or explore more Mathematics topics.
Related questions