Number System - Questions & Discussions

Naga, jus applying the theorem to check for lower primes 2, 3, 5, 7 and 11

for 2, 8 is perfectly divisible by 2
for 3, 88 is not perfectly divisible by 3..
for 5, 8888 is not perfectly divisible by 5
for 7, 888888 is perfectly divisible by 7
for 11, 8888888888 is perfectly divisible by 11

are we missing something in the theorem??
Regards
SK

valid for prime number greater than 5... oops i missed that
jain_ashu Says
This theorem is applicable only for prime numbers greater than 5.

naga25french Says
valid for prime number greater than 5... oops i missed that

Where do you guys refer all these theorems?
One from my side:

Q)In an integer d1d2...dk from left satisfy didi+1 for i even. How many integers from 1000 to 9999 have four distinct digits?


its quite to difficult to tell without option.. pls let us know the options if u have
Sahana Kavitha Says
Where do you guys refer all these theorems?



i read it some where two years back .. dont remember the source.. some forum page in orkut i think.. no real source of info

so logic is

observe anything everything
One from my side:
Q)In an integer d1d2...dk from left satisfy didi+1 for i even. How many integers from 1000 to 9999 have four distinct digits?


is it 5040?
naga25french Says
its quite to difficult to tell without option.. pls let us know the options if u have

One from my side:

Q)In an integer d1d2...dk from left satisfy didi+1 for i even. How many integers from 1000 to 9999 have four distinct digits?

the options are a) 630 b) 778 c) 882 d) none of these
Sahana Kavitha Says
is it 5040?

no its not.

Originally Posted by jain_ashu View Post
One from my side:

Q)In an integer d1d2...dk from left satisfy didi+1 for i even. How many integers from 1000 to 9999 have four distinct digits?


jain_ashu Says
the options are a) 630 b) 778 c) 882 d) none of these


Draft for your comments, ans 7(every 10)*8(every 100)*90 = 5040

1023-1032-1042-1052-----
1024-1034-1043-1053-----
1025-1035-1045-1054-----
1026-1036-1046-1056-----
1027-1037-1047-1057-----
1028-1038-1048-1058-----
1029-1039-1049-1059-----
7 + 7 + 7 + 7 +++++720 times
Originally Posted by jain_ashu View Post
One from my side:

Q)In an integer d1d2...dk from left satisfy didi+1 for i even. How many integers from 1000 to 9999 have four distinct digits?



Draft for your comments, ans 7(every 10)*8(every 100)*90 = 5040

1023-1032-1042-1052-----
1024-1034-1043-1053-----
1025-1035-1045-1054-----
1026-1036-1046-1056-----
1027-1037-1047-1057-----
1028-1038-1048-1058-----
1029-1039-1049-1059-----
7 + 7 + 7 + 7 +++++720 times

In 1023, 1 2 so the number cannot be counted. Similarly for other numbers.

A few doubts :-P

1.Form a subset of integers choosen b/w 1 to 3000 such that no 2 integer add up to amultiple of 9.wt can be the max no: of element in subset.
a.1668 b.1332 c.1333 d.1334

2.a triangular no:is defined as a no:which has a property of being expressed as a sum of consecutive natural nos starting with 1.how many trngular no: less than 1000 have the property that they r the difference of squire of 2 consecutive natural nos
a.20 b.21 c.22 d.23

3. highest power of 3 in exp 58!-38!

A few doubts :-P

3. highest power of 3 in exp 58!-38!


Its the highest power of the common factorial, hence
38/3 + 38/9 + 38/27 = 17

the highest power of 3 is 3^17

A few doubts :-P

1.Form a subset of integers choosen b/w 1 to 3000 such that no 2 integer add up to amultiple of 9.wt can be the max no: of element in subset.
a.1668 b.1332 c.1333 d.1334

3. highest power of 3 in exp 58!-38!

1.
option d. 1334
9a+1,9b+2,9c+3,9d+4 = 3000

a = 333
b = 334
c = 333
d = 333
total = 1333 + 1 = 1334

3.
38!*(3k-1)==>3^17
max power = 17
A few doubts :-P

2.a triangular no:is defined as a no:which has a property of being expressed as a sum of consecutive natural nos starting with 1.how many trngular no: less than 1000 have the property that they r the difference of squire of 2 consecutive natural nos
a.20 b.21 c.22 d.23


The sum of the consecutive no shall be a square, hence it is 21

3^2 --> (5,4)
5^2 --> (13,12)
7^2 --> (25,24)
9^2 --> (41,40)
11^2 --> (61,60)
13^2 --> (85,84)
15^2 --> (115,114)
.
.
.
.
43^2 --> (925,924)
45^2 --> (1013, 1012) >> 1000

any lucid method pls....
1.
option d. 1334
9a+1,9b+2,9c+3,9d+4 = 3000

a = 333
b = 334
c = 333
d = 333
total = 1333 + 1 = 1334

3.
38!*(3k-1)==>3^17
max power = 17


can you plz explain the first problem

Originally Posted by BIJAY PRASAD View Post
A few doubts

1.Form a subset of integers choosen b/w 1 to 3000 such that no 2 integer add up to amultiple of 9.wt can be the max no: of element in subset.
a.1668 b.1332 c.1333 d.1334

1.

option d. 1334
9a+1,9b+2,9c+3,9d+4 = 3000

a = 333
b = 334
c = 333
d = 333
total = 1333 + 1 = 1334

Not able to understand your solution, pls explain.. the highlighted part..
Originally Posted by BIJAY PRASAD View Post
A few doubts

1.Form a subset of integers choosen b/w 1 to 3000 such that no 2 integer add up to amultiple of 9.wt can be the max no: of element in subset.
a.1668 b.1332 c.1333 d.1334

1.

option d. 1334
9a+1,9b+2,9c+3,9d+4 = 3000

a = 333
b = 334
c = 333
d = 333
total = 1333 + 1 = 1334

Not able to understand your solution, pls explain.. the highlighted part..


wat i ve understood is that we need a subset of integers where no 2 integers add upto be a multiple of 9.....
so if we take integers of the form 9a+1,9b+2,9c+3,9d+4 nd choose any 2 integers it's sum would never be a multiple of 9
eg 9a+1+9b+2=9(a+b)+3 which is not a multiple of 9 similarly for the rest of the numbers
now if 9a+1 is taken as an integer then a can have a value where 1since the integer has to be less than 3000 nd more than 1
similarly we get for the rest of d value.......
in d end just add all d values........
hope it is clear now............
Originally Posted by BIJAY PRASAD View Post
A few doubts

1.Form a subset of integers choosen b/w 1 to 3000 such that no 2 integer add up to amultiple of 9.wt can be the max no: of element in subset.
a.1668 b.1332 c.1333 d.1334



wat i ve understood is that we need a subset of integers where no 2 integers add upto be a multiple of 9.....
so if we take integers of the form 9a+1,9b+2,9c+3,9d+4 nd choose any 2 integers it's sum would never be a multiple of 9
eg 9a+1+9b+2=9(a+b)+3 which is not a multiple of 9 similarly for the rest of the numbers
now if 9a+1 is taken as an integer then a can have a value where 1since the integer has to be less than 3000 nd more than 1
similarly we get for the rest of d value.......
in d end just add all d values........
hope it is clear now............

we can have one more number of the form 9k,
total = 1333 +1 = 1334
One from my side:

Q)In an integer d1d2...dk from left satisfy didi+1 for i even. How many integers from 1000 to 9999 have four distinct digits?

Puys pls try this...
the options are a) 630 b) 778 c) 882 d) none of these
Puys pls try this...
the options are a) 630 b) 778 c) 882 d) none of these


Is it option b) 778 ?