## rafeds08 3 years ago express in roster form: B={xlxE N and 6<x<10}

1. myininaya

Just list all the natural numbers in the interval (6,10)

2. rafeds08

B={7,8,9}

3. myininaya

Yep, that is right.

4. rafeds08

thanks

5. myininaya

np

6. rafeds08

what is np?

7. rafeds08

myininaya', what if the set Q of all prime numbers less than 10? can we consider the negative numbers?

8. myininaya

I think it depends on the definition of prime numbers your teacher chose. I choose the definition that they are natural numbers greater than 1 and are only divisible by 1 and itself. For example: 13 since 13 and 1 are it's only factors

9. UnkleRhaukus

$\{n\in \mathcal N |(1<n<10)∧(\forall x,y\in \mathcal N)[(xy=n)⇒(x=1∨y=1)]\}$

10. myininaya

So do you think you can now list the prime numbers between 1 and 10 (not including 10 since it doesn't say equal to)?

11. rafeds08

yap

12. rafeds08

A math teacher is preparing an exam each of his Algebra class. Math-alino and Math-matalino, covering topics A (circles) and B (inequalities). He wants to design the exams so that both classes will have the same number of questions on A and also on B. Each question on A is worth 15 points in section Math-alino and 20 points in section Math-matalino while each question on B is worth 10 points in section Math-alino and 5 points in section Math-matalino. If the total number of points in both exams is 100, how many questions should he ask on each topic?

13. rafeds08