Discussion about math, puzzles, games and fun.   Useful symbols: ÷ × ½ √ ∞ ≠ ≤ ≥ ≈ ⇒ ± ∈ Δ θ ∴ ∑ ∫ • π ƒ -¹ ² ³ °

You are not logged in.

## Post a reply

Write your message and submit
|
Options

## Topic review (newest first)

bobbym
2012-10-16 12:29:03

Hi juan;

For 1)

I am getting 399999960. I am assuming you want to use all seven numbers to form a seven digit number.

For 2) I am getting 578.

For 3) I am getting 4672.

anonimnystefy
2012-10-16 05:56:43

#### bob bundy wrote:

Q1.  There are 7 digits.  Pretend they are all different, a,b,c,d,e,f,g say.

Find all the possibilities:

a, ab, abc, .......fg, g

Now allow for the repeats by dividing  (eg if all 4s then divide by 4!)

Might be easier to count by taking all the 4s; then only three 4s then only two etc.

Q2. No number can be over 10 or under 1.

So 10 + 1 + 1
9 + 2 + 1
9 + 1 + 2

etc.  It's not so bad to continue like this, is it?

That should show you a generating technique which will make Q3 easy.

Bob

We don't need the number of those kind of nos in tthe first problem. And in the second problem, the numbers an also take on a negative value...

bob bundy
2012-10-16 05:52:04

Q1.  There are 7 digits.  Pretend they are all different, a,b,c,d,e,f,g say.

Find all the possibilities:

a, ab, abc, .......fg, g

Now allow for the repeats by dividing  (eg if all 4s then divide by 4!)

Might be easier to count by taking all the 4s; then only three 4s then only two etc.

Q2. No number can be over 10 or under 1.

So 10 + 1 + 1
9 + 2 + 1
9 + 1 + 2

etc.  It's not so bad to continue like this, is it?

That should show you a generating technique which will make Q3 easy.

Bob

anonimnystefy
2012-10-16 05:47:48

For (1): Must all the digits be used in making one number?

juan
2012-10-16 05:32:09

(1) The sum of all no. that can be formed by  using the digits

(2) Total no. of positive Integer solution of

(3) Total no. of positive Integer solution of