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: 22,664

NT # 1

What is the highest power of 7 in 5000!?

It is no good to try to stop knowledge from going forward. Ignorance is never better than knowledge - Enrico Fermi.

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

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: 22,664

It is no good to try to stop knowledge from going forward. Ignorance is never better than knowledge - Enrico Fermi.

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

Offline

**krassi_holmz****Real Member**- Registered: 2005-12-02
- Posts: 1,905

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: 22,664

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?

It is no good to try to stop knowledge from going forward. Ignorance is never better than knowledge - Enrico Fermi.

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

Offline

**krassi_holmz****Real Member**- Registered: 2005-12-02
- Posts: 1,905

6^2=3^2 2^2

a=3*11^2

IPBLE: Increasing Performance By Lowering Expectations.

Offline

**ganesh****Moderator**- Registered: 2005-06-28
- Posts: 22,664

krassi_holmz, you get this award!

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

Offline

**ganesh****Moderator**- Registered: 2005-06-28
- Posts: 22,664

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?

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

Offline

**krassi_holmz****Real Member**- Registered: 2005-12-02
- Posts: 1,905

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

IPBLE: Increasing Performance By Lowering Expectations.

Offline

**ganesh****Moderator**- Registered: 2005-06-28
- Posts: 22,664

Correct!

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

Offline

**ganesh****Moderator**- Registered: 2005-06-28
- Posts: 22,664

NT # 4

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

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

Offline

**krassi_holmz****Real Member**- Registered: 2005-12-02
- Posts: 1,905

105/4

IPBLE: Increasing Performance By Lowering Expectations.

Offline

**ganesh****Moderator**- Registered: 2005-06-28
- Posts: 22,664

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

Offline

**krassi_holmz****Real Member**- Registered: 2005-12-02
- Posts: 1,905

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: 22,664

krassi_holmz,

What about 105/288?

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

Offline

**ganesh****Moderator**- Registered: 2005-06-28
- Posts: 22,664

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.

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

Offline

**krassi_holmz****Real Member**- Registered: 2005-12-02
- Posts: 1,905

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: 22,664

I concede, you are correct krassi_holmz, well done!

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

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, 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, 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