## anonymous one year ago counting question

1. anonymous

2. anonymous

3. IrishBoy123

you have 1AB2 and 1CD5

4. IrishBoy123

A,B,C,D are all somewhere in 0,...9

5. IrishBoy123

can you take it from there?

6. IrishBoy123

7. anonymous

|dw:1441103308403:dw|

8. anonymous

can i solve it by scientific calc

9. IrishBoy123

how many ways to choose A, then for each A you choose, how many ways to pick B repeat for C,D

10. anonymous

by npr or ncr

11. IrishBoy123

you can do it in your head if you know how to do it

12. IrishBoy123

nCr

13. anonymous

NO @Nourage

14. IrishBoy123

but really, it's easier than that

15. anonymous

how i do it by ncr

16. IrishBoy123

you have 10 ways to choose A, right?

17. anonymous

|dw:1441103482580:dw|

18. IrishBoy123

$C_{1}^{10}$!!

19. IrishBoy123

ie you don't need it

20. IrishBoy123

then once you have chosen A, you have 10 ways to choose B

21. IrishBoy123

@ASAAD123 's drawing is a really nice clue

22. anonymous

i want to do it by calc how

23. anonymous

can u tell me

24. anonymous

you don't need a calc, you need think about the problem.

25. anonymous

i can solve it by think but i want to know how to do it by calc

26. anonymous

bec think take alot of time

27. anonymous

can u hlp

28. anonymous

by calc ncr or npr and how

29. anonymous

for the first digit, you have 1 way (1), for second and third digit you have 10 ways(0-9), and for last digit you have 2 ways (2 or 5). then use product rule. that's it

30. anonymous

i need to know how to do it by ncr or npr can u hlp

31. anonymous

and why (0-9)

32. anonymous

can u tell me how to do it by ncr or npr@IrishBoy123

33. anonymous

@IrishBoy123

34. anonymous

@ganeshie8 can u hlp

35. anonymous

$1C1 \times 10C1 \times10C1\times 2C1$

36. anonymous

37. anonymous

ok but why u do(0-9) why not(0-8) or any thing like this

38. anonymous

0 is neither negative nor positive. sometimes is is counted as positive

39. anonymous

ok but why u use 9 not other digit

40. anonymous

there are only 10 digits (0,1,2,3,4,5,6,7,8,9)

41. anonymous

ok why u chose 9 not 1 or 2 or 3or other digit

42. anonymous

every number in the world is contained one or more of these digits.

43. anonymous

for example: 1092 1912 1475

44. anonymous

u chose 9 bec it is the end of the numer right or wrong

45. anonymous

the end of digits

46. anonymous

bec the numbers start from 0 to 9

47. anonymous

ok digits from 0 to 9 rihgt or wrong

48. anonymous

ok mr asaad can u tell me why u 1*10*10*2 and what is the Relationship between this and (0-9) that u wrote it 2nd

49. anonymous

50. anonymous

hlp

51. mathmate

@Nourage These nice people have been trying to help you do the counting, exactly as you posted "counting question". Be patient and listen to the explanations. Calculations come later, when you understand how you count. In counting as in ALL math problems, blindly applying a formula does not work. You need to understand the problem first, then try to understand HOW you want to solve the problem. Formulas are just tools to help you when you need it.