We use cookies to personalise content and advertisements and to analyse access to our website. Furthermore, our partners for online advertising receive pseudonymised information about your use of our website.
Please click on "Accept cookies" if you agree to the setting of cookies. Cookies that do not require consent remain unaffected by this, see
cookie policy and privacy policy.
DECLINE COOKIES

(1) What is the greatest number of points of intersection that can occur when 2 different circles and 2 different straight lines are drawn on the same piece of paper?

(2) Let p be a prime number between 40 and 60. What is the probability that p+12 is also a prime number? Express your answer as a common fraction

tertre Dec 3, 2017

#1**+1 **

(1) I believe the answer to this is 11

The circles can intersect at 2 points

Each line can intersect each circle twice = 8 points

And as long as the lines do not intersect at any of the other points, they can intersect at 1 additional point

(2) Primes between 40 and 60 are

41 , 43 , 47, 53 , 59

And adding 12 to these =

53 , 55 , 59, 65 , 71

And 3 out of the 5 are prime [ 53, 59, 71 ]

So....the probability that p + 12 is prime is 3 / 5

CPhill Dec 3, 2017