# Math Is Fun Forum

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

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## #1 Re: Jai Ganesh's Puzzles » Set Language » 2008-08-28 20:21:04

In a survey of 100 persons it was found that 39 subscribed to TV Guide, 26 subscribed to Time and 6 subscribed to Scientific American. A total of 15 subscribed to at least two of these magazines and 2 subscribed to all three. How many persons did not subscribe to any of the three?

## #2 Re: Jai Ganesh's Puzzles » Set Language » 2008-08-28 20:08:12

In a survey of 200 students of a higher secondary school, it was found that 120 studied mathematics; 90 studied physics; 70 studied chemistry; 40 studied mathematics and physics; 30 studied physics and chemistry; 50 studied chemistry and mathematics, and 20 studied none of these subjects. Find the number of students who studied all the three subjects?

## #3 Re: Jai Ganesh's Puzzles » Number Theory » 2008-08-27 14:17:29

In a certain system product of 44*11 is represented s 2124 find how 1453 can be represented in decimal system ?

## #4 Re: Jai Ganesh's Puzzles » Permutations and Combinations » 2008-08-21 19:24:18

There are 10 boxes numbered 1, 2, 3, 10. Each box is to be filled up either with a black or a white ball in such a way that at least 1 box contains a black ball and the boxes containing black balls are consecutively numbered. The total number of ways in which this can be done is..

## #5 Re: Jai Ganesh's Puzzles » Speed, Distance, Time » 2008-08-20 20:05:07

Rohan fires two bullets from the same place at an interval of 12 minutes but Raju sitting in a train approaching the place hears the second report 11 minutes 30 seconds after the first. What is the approximate speed of train (if sound travels at the speed of 330 meters per seconds)?

## #6 Re: Jai Ganesh's Puzzles » Permutations and Combinations » 2008-08-20 19:58:10

There are 3 boys and 3 girls. In how many ways can they be arranged so that each boy has at least one girl by his side?

## #7 Re: Jai Ganesh's Puzzles » *** Problems » 2008-08-13 04:25:58

Let the quadratic ax^2 + bx + c be such that a, b, c are distinct and each of a, b, c belong to {1, 2, 3, ..., n} such that x+1 divides ax^2 + bx + c.
If the number of such quadratic polynomials are < 99, then max (n) is ??

## #8 Re: Jai Ganesh's Puzzles » Speed, Distance, Time » 2008-08-11 17:16:53

ZHero wrote:

In 3 hrs the thief has run 120 km. Relative speed of thief and police is 10 kmph. So, police will take 12 hrs to catch the thief and thus the dog will run for the same amount of time (no matter in what direction!)!
Hence, the total distance travelled by the dog is 12*60=720 km!

720 is the total distance covered by dog, the question asks the distance covered by dog in direction of the thief...  you have to remove the distance which dog covered coming back to police each time after seeing the thief...

## #9 Re: Jai Ganesh's Puzzles » Speed, Distance, Time » 2008-08-11 16:15:08

A thief escaped from police custody. His speed is 40 km/hr. The police realized it after 3 hr and started chasing him in the same direction at 50km/hr. The police had a dog which could run at 60 km/hr. The dog would run to the thief and return to the police and then would turn back towards the thief and so on until the thief is caught. Find the total distance travelled by the dog in the direction of the thief.

## #10 Re: Jai Ganesh's Puzzles » Number Theory » 2008-08-11 15:04:11

How many numbers less than 10^5 have the sum of digits equal to 10

## #11 Re: Jai Ganesh's Puzzles » Number Theory » 2008-08-11 01:20:52

How many natural numbers having at most six digits have the sum of their digits as at most six?

## #12 Re: Jai Ganesh's Puzzles » Number Theory » 2008-08-07 21:00:16

What is the sum of the sum of the sum of the digits of 55!?

## #13 Re: Jai Ganesh's Puzzles » Coordinate Geometry » 2008-08-06 00:40:20

What is the distance in cm between two parallel chords of lengths 32 cm and 24 cm in a circle of radius 20 cm?

## #14 Re: Jai Ganesh's Puzzles » Set Language » 2008-08-05 14:11:09

In a survey of political preference,78% of those asked were in favoured of at least one of the proposals: I, II and III. 50% of those asked favored proposal III. If 50% of those asked favoured all three of the proposals, what percentage of those asked favoured more than one of the 3 proposals.

## #15 Re: Jai Ganesh's Puzzles » Number Theory » 2008-08-05 13:39:09

The following table gives the details of the ages and heights of the boys and girls attending a hobby camp. The height (in cm) of each boy/girl is an integer.

Age Group                                        Boys                                            Girls

(Age(A),in years)

A<=10                                       8(120,130,150)                            10(110,130,140)

11<=A<=13                             10(130,150,160)                              8(120,140,150)

14<=A<=16                               6(150,160,180)                              6(140,150,170)

A>16                                          5(170,180,200)                             8(150,160,180)

In the above table, the number mentioned outside the brackets in each cell gives the number of boys (or girls) in that age group and the values mentioned inside the brackets give the minimum height, the average height and the maximum height of the persons in that group, in that order.

For example, of the eight boys who are of age not more than 10 years, the minimum height of any boy is 120 cm, the average height of all the boys is 130 cm and the maximum height of any boy is 150 cm.

1)A team is to be selected from the boys in the camp who were of age 13 years or below. If only boys who are 140 cm or more in height can be selected, the number of boys who can be selected is at most.

2)If a team of girls of age 13 years or less is to be selected, with the condition that all the girls who are 130 cm or more in height must be selected, what is the minimum number of girls selected?

## #16 Re: Jai Ganesh's Puzzles » Number Theory » 2008-08-05 02:20:18

Find the remainder when 9*5^43 divided by 1000.

Do we have any source to find all sorts of such questions....help will be really appriciated

## #18 Re: Puzzles and Games » New Puzzles » 2008-08-01 05:18:12

John, Pete, Tom, George, and Steve are brothers. One day, one of them broke a window. When their father asked them who did it, they gave the following answers:
John: "It was Pete or Tom."
Pete: "It was neither George nor me."
Tom: "Both of you are lying."
Steve: "No, only one of them is lying."
George: "No, Steve, you are wrong."
Then their mother added: "Three of my sons are telling the truth, but I do not believe what the two others said."

My Question is Who broke the window?

## #19 Puzzles and Games » New Puzzles » 2008-08-01 05:17:57

Sudeep
Replies: 4

Hi Guys,

Please try these and give description of each and every problem you solve.

Thnx.

## #20 Re: Jai Ganesh's Puzzles » Permutations and Combinations » 2008-07-22 17:07:15

krassi_holmz wrote:

They must be tigether so we have 3 subjects that must be arranged:
AEM
AME
EAM
EMA
MAE
MEA

the answer should be !6 * !3 *!2 * !3

the books can be arranged among themselves as
!6  Economics,
!3 on Mathematics
!2 on Accountancy

and !3 among themselves

## #21 Re: Jai Ganesh's Puzzles » Number Theory » 2008-07-22 01:00:34

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?

## #22 Re: Jai Ganesh's Puzzles » Number Theory » 2008-07-22 00:52:38

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

thnx anyway

## #23 Re: Jai Ganesh's Puzzles » Number Theory » 2008-07-21 21:37:22

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

## #24 Re: Jai Ganesh's Puzzles » Number Theory » 2008-07-21 14:35:10

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.