Math Is Fun Forum

Transcending

Member

Registered: 2015-06-15

Posts: 12

Combinations and Permutations

For all integer combinations xy for 2 ≤ x ≤ 6 and 2 ≤ y ≤ 4:

22=4, 23=8, 24=16
32=9, 33=27, 34=81
42=16, 43=64, 44=256
52=25, 53=125, 54=625
62=36, 63=216, 64=1296

The sequence generated contains 15 unique terms:
4, 8, 9, 16, 25, 27, 36, 64, 81, 125, 216, 256, 625, 1296

How many unique integers are in the sequence generated by xy for 2 ≤ x ≤ 99 and 2 ≤ y ≤ 99?

A•     9 045
B•     7 829
C•     7 090

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: Combinations and Permutations

Hi;

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In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Transcending

Member

Registered: 2015-06-15

Posts: 12

Re: Combinations and Permutations

bobbym,

Thank you.
I got 9604
X(number of term)=99-2+1=98
       Y(number of term)=99-2+1=98
XY(number of unique integer) =98×98=9604

Please advice me how to go about this question.
Also I noticed you responded to the other forum questions titled Combinations and Permutations. Thank you.
Can you teach me how to reason thru those questions?

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: Combinations and Permutations

Hi;

The problem needs to be reworded first. It should be x^y rather than xy.

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In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.