Brain Teasers

JaneFairfax · 2008-05-27 01:11:10

MathIsFun has a similar puzzle: One and a Half Hens
http://www.mathsisfun.com/puzzles/one-a … ution.html

Last edited by JaneFairfax (2008-05-27 04:49:49)

Jai Ganesh · 2008-05-27 02:41:55

I am really sorry, JaneFairfax!
I thought you had answered #69 when you had actually answered #68. I sincerely apologize for that hasty post. I tend to make mistakes when I try to be quick. You are perfectly right!
Speed and accuracy don't go hand in hand, when thinking is involved.

JaneFairfax · 2008-05-27 12:05:25

Jai Ganesh · 2008-05-27 18:43:57

Answer to #69:
Excellent, JaneFairfax!

JaneFairfax · 2008-05-28 07:28:33

#45 is similar to #68.

Jai Ganesh · 2008-05-28 21:52:14

Yes, it is, JaneFairfax! I didn't notice that!

#70. An equilateral triangle BPC is drawn inside a square ABCD. What is the value of the angle APD in degrees?

Jai Ganesh · 2008-05-28 23:16:21

The vertices of the square are A, B, C, and D. The vertices of the equilateral triangle are B, P, and C. Hence, one of the sides of the equilateral triangle is BC. The square also has BC as one of its sides.

Jai Ganesh · 2008-05-28 23:55:43

#71. Consider the set S = {1, 2, 3, ...., 1000}. How many Arithmetic Progressions can be formed from the elements of S that start with 1 and end with 1000 and have at least 3 elements?

JohnnyReinB · 2008-05-29 00:01:03

JaneFairfax · 2008-05-29 00:21:09

Jai Ganesh · 2008-05-29 02:28:45

Answers to #70, and #71:

Excellent, JaneFairfax! Keep it up!

Jai Ganesh · 2008-05-29 02:58:55

#72. Eric wrote down all the possible three digit numbers with distinct digits on a blackboard. Brian erased all the numbers on the blackboard whose first and last digits were either both odd or both even. How many numbers are left on the blackboard?

JaneFairfax · 2008-05-29 03:26:38

Can the three-digit numbers start with 0?

Jai Ganesh · 2008-05-29 03:32:21

No, they wouldn't be three digit numbers then!

mathsyperson · 2008-05-29 03:44:51

This smilie is expressing the answer by interpretive dance.

JaneFairfax · 2008-05-29 10:44:03

ganesh wrote:

No, they wouldn't be three digit numbers then!

I wasnt sure if you meant numbers as in integers or numbers as in numeric expressions. For example, 012 may be a two-digit integer, but as a numeric expression, it has three digits. (It could be the combination to a lock, say.) I just want to be sure which one (integers or numeric expressions) you meant.

Anyway

Last edited by JaneFairfax (2008-05-29 11:52:51)

mathsyperson · 2008-05-29 11:03:42

Jane, you've worked out the amount of numbers that got erased.

JaneFairfax · 2008-05-29 11:56:24

Last edited by JaneFairfax (2008-05-29 21:43:03)

Jai Ganesh · 2008-05-29 18:00:09

Answer to #72:
Brilliant, JaneFairfax!

Jai Ganesh · 2008-12-01 03:21:13

#73. If the persons A and B have incomes in the ratio 7 : 5 and
expenditures in the ratio 3 : 2 and each one of them saves $ R, then,
what is the income of A?

#74. At 7 : 55 a.m. a police jeep started chasing a stolen car
running at 85 km/hr ahead of it by 5 km. At what time will the police jeep
overtake the stolen car, if its speed is 100 km/hr?

#75. It takes the same time to go 20 km downstream as it takes
to go 12 km upstream. If the speed of the boat used is 8 km/hr in still
water, the speed of the stream (in km/hr) is____________.

Jai Ganesh · 2008-12-15 02:06:11

#76. 3 men and 5 boys can do nineteen-twentieth of a piece of work in 3 days. 4 men and 8 boys can do fourteen-fifteenth of the same work in 2 days. In what time can a boy do the whole work?

#77. A tap P can fill a tank in 10 hours Another tap can empty the tank in 11 hours. The taps P and Q are opened alternately for one hour each. If P is opened first, after how many hours will the empty cistern get filled?

#78. A boy running up a staircase finds that when he goes two steps at a time, there is one step leftover. When he goes up three at a time, two steps are leftover and when he goes up four at a time, there are three left over. What is the minimum number of total stairs?

careless25 · 2008-12-24 06:09:35

Last edited by careless25 (2008-12-24 06:10:16)

Jai Ganesh · 2008-12-24 16:53:13

careless25,
Your edited answer is correct!
W E L L D O N E!!!

You also deserve this award for saying you edited the answer

Jai Ganesh · 2008-12-28 01:52:52

#79. A side of a cube is √3. What is the maximum length of a stick it can contain?

#80. What is the value of xyz if

?

#81. A gives half his salary to his wife, half of the remaining salary to his son and one-third of what remains to his daughter. He is left with $500. What is his salary?

Jai Ganesh · 2008-12-28 02:03:02

Complete the series/Fill in the blank:-

#82. 1, 16, 81, 256, ___.

#83. 720, 360, ___, 30, 6, 1.

#84. 5, 8, 16, 19, 38, 41, 82, ____.

#85. 11, 13, 17, 19, ____, 25, 29.

Math Is Fun Forum

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