How Many Numbers Between 50 & 80?

Question

How many numbers between 50 and 80 can be written using the digits 0,1,2,3,4 if no digit is repeated in any number?

Answer 1

None. There are no numbers between 50 and 80 that do not have a digit higher than 4. All the numbers between 50 and 80 start with a 5, 6, or a 7.

Answer 2

None, because all the numbers between 50 and 80 start with a 5, a 6 or a 7.

Answer 3

Between 50 and 80, there are 29 digits out of which only 12 can be written using any of 0, 1, 2, 3 and 4 ( 51,52,53,54,61,62,63,64,71,72,73 and 74)

The answer is therefore 12 digits

Answer 4

Let's say there have been 3 of these prime numbers, p1, p2 and p3. Then P = p1*p2*p3 Its reasons are first of all the primes themselves, p1, p2 and p3. Then all the combinations of two of them: p1*p2, p1*p3, p2*p3 Then the combo of all three, p1*p2*p3. Whole: three + 3 + 1 = 7.(i am now not counting 1 as probably the most numbers that divides P, however probably you are presupposed to). Now, you can have more than three primes. Begin via figuring out how many primes there are between 50 and 80. Then add up that number n, with the number of pairs, nC2, the number of agencies of 3, nC3, the quantity of groups of 4, nC4, and many others. I will be able to see a shortcut. The sum of nC0 + nC1 + nC2 + ... + nCn is the same as 2^n. So when you depart off the first one (nC0), the outcome is 2^n - 1. In my example with 3 primes, the sum is 2^three - 1 = eight - 1 = 7.

Answer 5

none i guess