×

# Arithmetic Mean!

The arithmetic mean of a number of pairwise distinct prime numbers is 27. Determine the biggest prime among them.

Note by Ayush Rai
6 months, 3 weeks ago

Sort by:

This problem came in NMTC 2015. The prime numbers must be less than 54. Listing first few possibilities 53 and 1, 52 and 2, 51 and 3, 50 and 4, 49 and 5, 48 and 6, 47 and 7. Only the pair 47 and 7 are both primes and 47 is the biggest. · 6 months, 3 weeks ago

You seem to be assuming there are only two prime numbers, when the question doesn't explicitly state that.

Otherwise, there can be other solutions like $$(3,7,71)$$ · 6 months, 3 weeks ago

It clearly states pair wise that means only two prime numbers. · 6 months, 3 weeks ago

Nope. Pair wise distinct does not mean only two. Pair wise distinct means that given a set of elements, no two elements (pair) of the set are the same. It does not restrict the number of elements in the set.

https://proofwiki.org/wiki/Definition:Distinct/Plural/Pairwise_Distinct · 6 months, 3 weeks ago

definition:A set of objects is pairwise distinct if each pair of elements of that set is distinct.
It clearly states a pair of elements which means two elements. · 6 months, 3 weeks ago

each pair. Not a pair. · 6 months, 3 weeks ago

that makes no difference. · 6 months, 3 weeks ago

You can check the top comment here or this. Notice how none of them refer to only two elements when talking about pairwise distinct elements. · 6 months, 3 weeks ago

I still don't agree with you. · 6 months, 3 weeks ago

Sure. No problem. · 6 months, 3 weeks ago

you are absolutely correct.Did you appear for the NMTC 2nd level test? · 6 months, 3 weeks ago

nope. I came to know about this exam this year only. Have you written it? · 6 months, 3 weeks ago

Can solve the other set of problems?their also from NMTC. · 6 months, 3 weeks ago