Brain Teasers

Jai Ganesh · 2009-01-12 17:24:32

Answers to #142 and #143:-
Perfectly right, JaneFairfax!

Jai Ganesh · 2009-01-12 18:59:32

#145. A can do a piece of work in 120 days and B can do it in 150 days. They work together for 20 days. Then B leaves, and A continues alone. 12 days after that, C joins A and the work is completed in 48 days more. In how many days can C do it if he works alone?

Jai Ganesh · 2009-01-12 20:18:17

#146. A and B can do a piece of work in 12 days, and B and C can do it together in 15 days. If A is twice as good as a workman as C, in how many days would B alone do the work?

#147. A, B, and C enter into a partnership. A contributes one-third of the capital while B contributes as much as A and C together contributed. If the profit at the end of the year amounted to $840, how much would each of them receive (the amount is shared proportionate to the capital)?

#148. A and b enter into a partnership. A provides whole of the capital amounting to $45,000 with the conditions that the profits is to be equally divided and that B pays A interest on half the capital at 10% per annum, but receives $120 per month for running the business. Find their total yearly profit if B's income if half of A's income.

#149. R and S are partners sharing profits and losses in the ratio 2:1. They admit T into the partnership giving him one-fifth share in profits which he acquires from R and S in the ratio 1:2. Calculate the new profit sharing ratio.

#150. Find the wrong number in the series:-
(a) 2, 5, 8, 11, 16
(b) 8, 10, 14, 18, 28, 34, 50, 66
(c) 36, 28, 26, 22, 21
(d) 5, 6, 7, 8, 10, 11, 14, 16

Jai Ganesh · 2009-01-13 02:13:34

#151. Complete the series:-
(a) 165, 195, 255, 285, 345, ____
(b) 2, 4, 12, 48, 240, ____
(c) 10, 5, 13, 10, 16, 20, 19, ____
(d) 2, 5, 9, 19, 37, _____

#152.At what time between 2 and 3 o'clock would the minute and hour hands of a clock overlap?

JaneFairfax · 2009-01-13 14:26:22

Jai Ganesh · 2009-01-13 17:37:59

Answers to #145, #146, and #149:-
(Please note, you have wrongly mentioned #140 instead of #149)

All the three answers are correct!

JaneFairfax · 2009-01-14 12:25:48

Jai Ganesh · 2009-01-14 20:25:32

Answer to #152:-
Correct, JaneFairfax!

Jai Ganesh · 2009-01-14 23:19:32

#153. What is the value of

?

#154. When a certain number is multiplied by 13, the product consists entirely of fives. What is the smallest such number?

#155. When 187, 233, and 279 are divided by a number, the same remainder is obtained in each case. Find the greatest such number?

JaneFairfax · 2009-01-15 07:06:40

Jai Ganesh · 2009-01-16 01:53:53

Answers to #153, #154, and #155:-
All correct, JaneFairfax!

Jai Ganesh · 2009-01-16 03:51:15

#156. Triangle ABC is inscribed in a semi-circle in which AB is the diameter and both AC and BC are of length

units each. If the triangle is painted green and the remaining portion painted blue, what is the area of the portion painted blue?

#157.The vertex O of a square MNOP is located at the center of a circle. If a diagonal of the square, NP, is

units long, what is the perimeter of the square MNOP?

#158. Two fences in a field meet at an angle of 120°. A cow is tethered at their interesction with a 15 meter rope. Over how many square meters of area can the cow graze?

JaneFairfax · 2009-01-16 09:04:16

careless25 · 2009-01-16 13:43:52

Jai Ganesh · 2009-01-17 04:02:06

Answers to #151, #156, #157, and #158:-
careless25, Answer to #151 is 75% correct. That is all that you answered are corrected.
Regarding #150, I shall reply in detail tomorrow.

JaneFairfax,
Answers to #157 and #158 correct. 66.67%
Please check your answer #156.

JaneFairfax · 2009-01-17 04:31:46

Argh! I forgot it was only a semicircle; I imagined a full circle instead.

Jai Ganesh · 2009-01-17 16:53:03

Answer to #156:-
This time, you're correct.
G o o d!

Jai Ganesh · 2009-01-17 19:22:00

#159. If

is the smallest number divisible by all the natural numbers from 1 to n, for what maximum value of n would
?

Jai Ganesh · 2009-01-17 23:46:57

#160. How many consecutive zeros would 10,000! end in?

#161. a, b, and c are even numbers and x, y, and z are odd numbers. Which of the following equation/equations is/are certainly not possible?
I.

II.
III.

(a) Only II (b) Only III (c) All of the three (d) Only II and III.

#162. What is the number of positive integers less than or equal to 100 which are not divisible by 2, 3, or 5?

Jai Ganesh · 2009-01-18 00:36:55

#163. If a, b, and c are in Harmonic Progression, then

are in
(1) Arithmetic Progression
(2) Geometric Progression
(3) Harmonic Progression
(4) None of these

#164. If x, y, and z are positive real numbers such that

,
what is the least value of ?

#165. An infinite Geometric Progression has first term a and sum to infinite terms equal to 4. Then, a lies in the interval
(1)

(2)
(3)
(4)

#166. If

are in Arithmetic Progression and a,b,c>0, then what is the least value of a+b+c?

#167. What is the nth term of a series if the sum of n terms of a series is given by

?

JaneFairfax · 2009-01-18 11:12:57

Last edited by JaneFairfax (2009-01-19 03:03:33)

Muggleton · 2009-01-18 11:56:32

Last edited by Muggleton (2009-01-18 12:46:57)

JaneFairfax · 2009-01-18 12:12:43

Last edited by JaneFairfax (2009-01-19 03:03:51)

Jai Ganesh · 2009-01-19 02:58:32

Answers to #159, #160, #161, #162, #164, and #167:-
Muggleton, Excellent! Your answer to #164 is correct!
JaneFairfax, Excellent!
Yours answers to #160, #161, #162, and #167 (not #165 as mentioned by you) are correct!
Please check your answer to#159.

!!!

JaneFairfax · 2009-01-19 03:17:29

Math Is Fun Forum

#251 2009-01-12 17:24:32

Re: Brain Teasers

#252 2009-01-12 18:59:32

Re: Brain Teasers

#253 2009-01-12 20:18:17

Re: Brain Teasers

#254 2009-01-13 02:13:34

Re: Brain Teasers

#255 2009-01-13 14:26:22

Re: Brain Teasers

#256 2009-01-13 17:37:59

Re: Brain Teasers

#257 2009-01-14 12:25:48

Re: Brain Teasers

#258 2009-01-14 20:25:32

Re: Brain Teasers

#259 2009-01-14 23:19:32

Re: Brain Teasers

#260 2009-01-15 07:06:40

Re: Brain Teasers

#261 2009-01-16 01:53:53

Re: Brain Teasers

#262 2009-01-16 03:51:15

Re: Brain Teasers

#263 2009-01-16 09:04:16

Re: Brain Teasers

#264 2009-01-16 13:43:52

Re: Brain Teasers

#265 2009-01-17 04:02:06

Re: Brain Teasers

#266 2009-01-17 04:31:46

Re: Brain Teasers

#267 2009-01-17 16:53:03

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#268 2009-01-17 19:22:00

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#269 2009-01-17 23:46:57

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#270 2009-01-18 00:36:55

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#271 2009-01-18 11:12:57

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#272 2009-01-18 11:56:32

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#273 2009-01-18 12:12:43

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#274 2009-01-19 02:58:32

Re: Brain Teasers

#275 2009-01-19 03:17:29

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