Brain Teasers

Jai Ganesh · 2009-02-19 02:13:18

#313. There are ten delegates representing five companies, equally. In how many ways can a group of four be selected and arranged such that there is not more than one representative belonging to the same company?

#314. The North-South Express is a pair of trans between Jammu and Chennai. A train leaves Jammu for Chennai exactly at 12 noon everyday of the week. Similarly, there's a train that leaves Chennai bound for Jammu on everyday of the week exactly at 12 noon. The time required by a train to cover the distance between Chennai and Jammu is exactly 7 days and 1 minute. Find the number of trains from Chennai to Jammu which a train from Jammu to Chennai would cross in completing its journey, assuming all the trains are on time.

#315. If n! contains 155 consecutive zeros at the end, how many values can n have?

#316. If n! contains 249 consecutive zeros at the end, how many odd values can n have?

#317. How many values of n are possible if n! contains 28 exponents of 4?

#318. A box contains 12 items and four are chosen at random from it and inspected. The box is rejected if more than one item is found to be faulty. Given that there are 3 faulty items in the box, find the probability of the box being accepted.

JaneFairfax · 2009-02-19 08:40:35

Last edited by JaneFairfax (2009-02-19 09:39:25)

careless25 · 2009-02-19 09:30:46

Jai Ganesh · 2009-02-20 01:04:34

Answers to #313, #315, and #318:
I cannot believe this! None of the answers are correct, JaneFairfax and careless25!
Of the wrong answers, #318 is the only one which is the result of a minor mistake. The other answers are nowhere near the correct ones!
Please try again!!!

Jai Ganesh · 2009-02-20 01:36:07

#319. A person went to a bank with exactly $1019, all in $1 bills. He gave the money to the cashier and said 'Put this money into a minimum number of bags in such a way that if I call and ask you for any integral number of Dollars up to #1019, you would be able to give me the exact amount by handing over one or more bags, without having to open any of the bags." What is the minimum number of bags required for the purpose?

#320. The roots of the quadratic equation x² - bx + c = 0 differ by 3. What is the relation between b, and c?

Last edited by Jai Ganesh (2009-02-20 20:45:52)

Jai Ganesh · 2009-02-20 02:24:32

#321. A, B, and C together earn $7600 and spend 70%, 75%, and 80% of their salaries respectively. If their savings are in the ratio 4:5:6 respectively, what is the salary of B?

#322. A and B are two fixed points 5 centimeters apart. C is a point on AB such that AC = 3 centimeters. If the lenght of AC is increased by 6%, by what percentage is the length of BC decreased?

#323. 1 liter of water is added to 5 liters of alcohol water solution containing 40% alcohol. What is the strength of alcohol in the new solution?

JaneFairfax · 2009-02-20 14:39:42

ganesh wrote:

Answers to #313, #315, and #318:
I cannot believe this! None of the answers are correct, JaneFairfax and careless25!

JaneFairfax · 2009-02-20 14:42:03

Jai Ganesh · 2009-02-20 20:45:24

Jai Ganesh · 2009-02-20 20:55:32

Answers to #322, and #323:-
Both correct, JaneFairfax!

#324. An equilateral triangle and a square are inscribed in a circle. What is the ratio of the area of the square to that of the equilateral triangle?

#325. Of all the 5 digit numbers that can be formed using the digits in the number system with Base 7, allowing repetition of digits, how many numbers would be even?

JaneFairfax · 2009-02-20 23:33:31

Jai Ganesh · 2009-02-21 00:29:38

Answer to #320:

#326. A bag contains Rs.50, Rs.20, and Rs.5 notes such that the number of Rs.50 notes is half the number of Rs.20 notes, and the number of Rs.5 notes is thrice the number of Rs.50 notes. If the total value of the notes in the bag is Rs.2,520, what is the number of Rs.50 notes?

#327. The weight of a single grape is 4 grams. Fresh grapes contain 81% water and dry grapes contain 24% water. What is the weight of dry grapes that can be obtained from 12,500 fresh grapes?

Jai Ganesh · 2009-02-21 23:04:01

#328. In a group of 500 students, there are 475 who can speak English and 200 who can speak French. What is the number of students who can speak English only if every student can speak one or both of these languages ?

#329. Between which rational numbers does x lie if

?

Jai Ganesh · 2009-02-22 19:40:42

#330. If the numbers given below are in binary system, what is the value of

?

#331. There are fourchairs with two chairs in each row. In how many ways can four persons be seated on the chairs, so that no chair remains unoccupied?

#332. In how many ways can the letters of the word CORPORATION be arranged so that the vowels always occupy even places?

#333. If all the permutations of the letters of the word 'LAGAN' are arranged as in a dictionary, then what is the rank of 'NAAGL'?

#334. Given

and
,
then what is equal to?

#335. Under what condition is the tangent to a given curve at a point perpendicular to the x-axis?

#336. In a Geometric progression with first term a and common ratio r, what is the Arithmetic Mean of the first five terms?

#337. What is the following product equal to?

?

#338. What is the value of x if

?

Jai Ganesh · 2009-02-26 21:08:32

#339. How many terms would the expansion of the following contain?

Jai Ganesh · 2009-03-02 01:58:54

#340. What is the last digit before the three zeros in 19! ?

#341. Find the sum of all odd three digit numbers that are divisible by 5.

Jai Ganesh · 2009-03-02 02:17:53

#342. What is the sum of the series

?

ZHero · 2009-03-02 04:28:17

My Attempts...

Jai Ganesh · 2009-03-02 17:09:14

Answers to #326, #327, #328, #329, #330, #331, #332, #334, #335, #337, #338, #339, #340, and #341:-
All answers other than #329 and 3340 are correct!
Keep it up, ZHero!

Jai Ganesh · 2009-03-02 17:19:21

#343. A uniform circular coin required too much metal relative to its value. Hence, it was decided to reduce the diameter of the coin by 10% and the thickness by 15%. Approximately, by how much percentage would the weight of the coin reduce if everything else about the coin remains unchanged?

#344. A and B solve a quardratic equation. A makes a mistake in the constant term and gets the roots as 5 and -3. B makes a mitake in the coefficient of x and gets the roots as 1 and -3. What are the correct roots of the quadratic equation?

#345. A worker was engaged for a job for 30 days on the condition that he would get a wage of $10 for everyday he works, but would have to pay a fine of $2 for his first day of absence. The fine would be doubled for the second day of absence and would be doubled for every additional day of absence., (Thus, he wouldhave to pay a fine of $2 for a day's absence, $4 for two days absence, $8 for three days absence, and so on). If he gets $114 at the end of 30 days, for how many days was he absent?

#346. How many 3 digit numbers are there which are divisible by 5 but not divisible by 25 and in which there are no repetition of digits?

JaneFairfax · 2009-03-03 00:03:33

Last edited by JaneFairfax (2009-03-03 00:05:48)

Jai Ganesh · 2009-03-03 02:04:03

Answer to #346:-
Correct, JaneFairfax!

Jai Ganesh · 2009-03-03 02:19:47

#347. If the area of the triangle ADE is 5 square units, and BD = 2 DE = 5 EC, what is the area of the triangle ABC?

Jai Ganesh · 2009-03-03 03:16:27

#348. Two regular polygons have number of sides in the ratio 4:5 and the measure of interior angles in the ratio 25:26 respectively. How many sides does the regular polygon with lesser number of sides have?

Jai Ganesh · 2009-03-03 20:12:30

#349. Which of the following numbers can possibly be the perfect square of a three digit odd number (some of the digits of the numbers have been hidden and replaed by 'x')?
(i) 65xxx
(2) 9xx1
(3) 10xxx4
(4) 9xxxxxx5

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