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

You are not logged in.

- Topics: Active | Unanswered

**ganesh****Moderator**- Registered: 2005-06-28
- Posts: 16,982

NT # 1

What is the highest power of 7 in 5000!?

Character is who you are when no one is looking.

Offline

**mathsyperson****Moderator**- Registered: 2005-06-22
- Posts: 4,900

5000! = 5000*4999*4998*4997*...*3*2*1.

Of all the numbers up to 5000, there are 5000/7 = 714 numbers that have 7 as a factor.

Of these 714, 714/7 = 102 of them have 7² as a factor.

Of these 102, 102/7 = 14 of them have 7³ as a factor.

Of these 14, 14/7 = 2 of them have 7[sup]4[/sup] as a factor.

Adding all of these gives 832, so that is the highest power of 7 in 5000!.

Why did the vector cross the road?

It wanted to be normal.

Offline

**ganesh****Moderator**- Registered: 2005-06-28
- Posts: 16,982

Character is who you are when no one is looking.

Offline

**krassi_holmz****Real Member**- Registered: 2005-12-02
- Posts: 1,906

There's a formula:

The higest power of p(prime) that divides n! is exactly:

*Last edited by krassi_holmz (2006-02-28 06:02:59)*

IPBLE: Increasing Performance By Lowering Expectations.

Offline

**ganesh****Moderator**- Registered: 2005-06-28
- Posts: 16,982

NT # 2

If both 11² and 3³ are factors of the number a * 4³ * 6² *13[sup]11[/sup], then what is the smallest possible value of a?

Character is who you are when no one is looking.

Offline

**krassi_holmz****Real Member**- Registered: 2005-12-02
- Posts: 1,906

6^2=3^2 2^2

a=3*11^2

IPBLE: Increasing Performance By Lowering Expectations.

Offline

**ganesh****Moderator**- Registered: 2005-06-28
- Posts: 16,982

krassi_holmz, you get this award!

Character is who you are when no one is looking.

Offline

**ganesh****Moderator**- Registered: 2005-06-28
- Posts: 16,982

NT # 3

A person starts multiplying consecutive positive integers from 20. How many numbers should he multiply before he will have a result that will end with 3 zeroes?

Character is who you are when no one is looking.

Offline

**krassi_holmz****Real Member**- Registered: 2005-12-02
- Posts: 1,906

20*21*23*24*25=127512000.

IPBLE: Increasing Performance By Lowering Expectations.

Offline

**ganesh****Moderator**- Registered: 2005-06-28
- Posts: 16,982

Correct!

Character is who you are when no one is looking.

Offline

**ganesh****Moderator**- Registered: 2005-06-28
- Posts: 16,982

NT # 4

What is the Least Common Multiple of 3/8, 5/36, 7/72 and 15/96?

Character is who you are when no one is looking.

Offline

**krassi_holmz****Real Member**- Registered: 2005-12-02
- Posts: 1,906

105/4

IPBLE: Increasing Performance By Lowering Expectations.

Offline

**ganesh****Moderator**- Registered: 2005-06-28
- Posts: 16,982

Character is who you are when no one is looking.

Offline

**krassi_holmz****Real Member**- Registered: 2005-12-02
- Posts: 1,906

What?

105/4=3/8*70=3/8*(2*5*7)

105/4=5/36*189=5/36*(3*3*3*7)

105/4=7/72*270=7/72*(2*5*3*3*3)

105/4=15/96*168=15/96*(7*3*2*2*2)

There ISN"T a number LESS than 105/4

IPBLE: Increasing Performance By Lowering Expectations.

Offline

**ganesh****Moderator**- Registered: 2005-06-28
- Posts: 16,982

krassi_holmz,

What about 105/288?

Character is who you are when no one is looking.

Offline

**ganesh****Moderator**- Registered: 2005-06-28
- Posts: 16,982

NT # 5

In an examination, the average marks obtained by students who passed was x%, the average marks obtained by students who failed was y% and the average marks of all the students who appeared for the examintion was z%. Find the percentage of students who failed in the examination in terms of x, y, and z.

Character is who you are when no one is looking.

Offline

**krassi_holmz****Real Member**- Registered: 2005-12-02
- Posts: 1,906

for NT 4:

(105/288):(3/8)=(35/36), which is not an integer???

IPBLE: Increasing Performance By Lowering Expectations.

Offline

**ganesh****Moderator**- Registered: 2005-06-28
- Posts: 16,982

I concede, you are correct krassi_holmz, well done!

Character is who you are when no one is looking.

Offline

**dan howitt****Member**- Registered: 2008-05-14
- Posts: 21

ganesh wrote:

krassi_holmz, you get this award!

Nice!

Dan Howitt

Offline

**Sudeep****Member**- Registered: 2008-07-21
- Posts: 20

Want help to solve few questions...simple for people having knowledge of Euler/ Fermet theorem but i am not that great at it...

1) Two numbers 698 and 450 when divided by a certain divisor leave remainders of 9 and 8 respectively. Find the largest such divisor.

Offline

**ZHero****Real Member**- Registered: 2008-06-08
- Posts: 1,889

If upon dividing 698 and 450, the divisor leaves remainders 9 and 8 respectively then it Must divide (698-9=689) and (450-8=442)!

Therefore, the required number is HCF of (689=13*53) and (442=2*13*17) which clearly is 13 !

Hence 13 is the answer...

If two or more thoughts intersect with each other, then there has to be a point.

Offline

**Sudeep****Member**- Registered: 2008-07-21
- Posts: 20

What is the minimum number of identical square tiles required to completely cover a floor of dimensions 8m 70 cm by 6m 38cm

Offline

**ZHero****Real Member**- Registered: 2008-06-08
- Posts: 1,889

Hi BumBumBhole!

From India haan?

Well.. Me too!

Jai Shiv Shankar!

Coming to the point..

Minimum number of squares will be needed if their size is maximum!

So required size of the squares is the square with sides of length which is HCF of 870cm & 638cm i.e. 29cm !

And number of squares is area of floor divided by area of tile..

=(870*638)/(29*29)

=330

Easy! Ain't it?

*Last edited by ZHero (2008-07-21 23:30:05)*

If two or more thoughts intersect with each other, then there has to be a point.

Offline

**Sudeep****Member**- Registered: 2008-07-21
- Posts: 20

ok learnt the approach the HCF will be 58 and not 29 so the answer will be 870*638/58^2 = 165

thnx anyway

Offline

**Sudeep****Member**- Registered: 2008-07-21
- Posts: 20

Another one ...the total number of factors of a natural number N is 45. What is the maximum number of prime numbers by which N can be divided?

Offline