i'm on a permutation unit in math and there is one question i have. the hardest ones for me are the problems where you have to find integers between certain boundaries that satisfy specific conditions. For example..:
How many positive integers less that 100 can be represented using the digits 1, 3, 7, 9.
So far I know that you have to somehow seperate the ones & the tens places and the formula for repeated numbers is involved.
If we have 6 burgers and 2 are cheese..blah blah blah
6! / 2! >>> b/c there are 2 cheese, they are repeated, etc.
work & explanation is greatly appreciated because i have to learn how to work this problem as efficently and as soon as possible. THANKS SO MUCH!!!
2007-03-28 14:09:54 · 4 answers · asked by bluenecklace 2 in Science & Mathematics ➔ Mathematics
The following site can help you a great deal with permutation questions.
Go to:
http://regentsprep.org/Regents/math/math-topic.cfm?TopicCode=permut
Guido
2007-03-28 14:13:57 · answer #1 · answered by Anonymous · 0⤊ 0⤋
Since they have to be less than 100, all are 2 digit numbers. SInce you have 4 different numbers, any of the 4 can be used 1st and any of the 4 2nd.
So 4(4) = 16 integers
2007-03-28 14:14:47 · answer #2 · answered by richardwptljc 6 · 0⤊ 0⤋
Imagine two boxes recpectivly a and b
condition : use only 1,3,7,9 digits with ''repetition'' and numbers < 100
Solution: boxe a : We have 4 possibility
boxe b : We have 4 possibility
So, We obtain 4 x 4 = 16 possibilities or 16 positive integers
2007-03-28 14:25:48 · answer #3 · answered by frank 7 · 0⤊ 0⤋
Use 1!3!7!9!
2007-03-28 14:14:10 · answer #4 · answered by Harry K 1 · 0⤊ 0⤋