Most younger students do not need the first hundred prime numbers chart although it is a very handy item for teachers with bright students :-) Use this prime number chart as an answer key or a practice worksheet. If 220 = 11*20, then 209, or 220 - 11, would contain one fewer 11. And the last is a printable list of the first 100 prime numbers to use in a binder or as a Math poster, etc. The one thing I'll add is that if you find it difficult to see that 209 is divisible by 11, you can start with a number in the neighborhood that we know is divisible by 11, such as 220, and extrapolate. Vincen has an excellent explanation here. One rule that can be useful is: if we want to know if x is a prime number, we have to divide it by all the primes between 2 and $$\sqrt\approx14.8$$ then we have to check only by 2, 3, 5, 7, 11 and 13. Hence the correct answer is the option B. Hence, we have to check just the following numbers: 203, 209, 211 and 217. M7MBA wrote:How many prime numbers exist between 200 and 220?Įxperts, what is the best approach that I could use to solve this PS question? May you give me some help?Ģ01, 207, 210, 213, 219 are divisible by 3 (because the sum of their digits is divisible by 3).
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