##### AoPS Subset Problem

 Algebra Tutor: None Selected Time limit: 1 Day

Let S be a subset of {1, 2, 3, 4...., 100}, containing 50 elements. How many such sets have the property that every pair of numbers in S has a common divisor that is greater than 1?

Aug 18th, 2015

HELLO...Monkeys

have one doubt  in your question

{1, 2, 3, 4...., 100}, containing 50 elements.

how only 50 elements will be  from  1 to 100  please  recheck the question and tell to me

thank you!!!!

Aug 18th, 2015

Aug 18th, 2015

ok.. thanx.. do you have any other  question ??

Aug 18th, 2015

A four by four grid of unit squares contains squares of various sizes (1 by 1 through 4 by 4), each of which are formed entirely from squares in the grid. In each of the 16 unit squares, write the number of squares that contain it. For instance, the middle numbers in the top row are 6s because they are each contained in one 1x1 square, two 2x2, two 3x3, and the one 4x4

What is the sum of all numbers in a 10x10 grid?

Aug 18th, 2015

the

1 ^2 + 2^2+ 3^2 --------  up to 10^2

by using  the formula of  the sum of square  of n natural no

S^2  =  n(n+1) (2n+1)/6

where n  = 10

10 *11*21/6 =     385

regarding further clarification please let me know ...

Thank you !!!

Aug 18th, 2015

No...ignore the question, can you understand the first part of it?

Aug 18th, 2015

sry .. not

Aug 18th, 2015

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Aug 18th, 2015
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Aug 18th, 2015
May 28th, 2017
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