# Math Is Fun Forum

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

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## #51 2006-03-15 06:16:52

Ikcelaks
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Registered: 2006-03-13
Posts: 8

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## #52 2006-03-15 08:12:45

Ikcelaks
Member
Registered: 2006-03-13
Posts: 8

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## #53 2006-03-15 16:15:35

Jai Ganesh
Registered: 2005-06-28
Posts: 47,758

### Re: *** Problems

Excellent, Ikcelaks! Your solution to Problem (11) is correct! I shall solve problem 8 and let you know whether you are correct!

It appears to me that if one wants to make progress in mathematics, one should study the masters and not the pupils. - Niels Henrik Abel.

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

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## #54 2006-03-15 16:17:01

Jai Ganesh
Registered: 2005-06-28
Posts: 47,758

### Re: *** Problems

***12

What is the sum of all the coefficients of

?

It appears to me that if one wants to make progress in mathematics, one should study the masters and not the pupils. - Niels Henrik Abel.

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

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## #55 2006-03-16 03:59:51

mathsyperson
Moderator
Registered: 2005-06-22
Posts: 4,900

### Re: *** Problems

Why did the vector cross the road?
It wanted to be normal.

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## #56 2006-03-16 04:32:20

Jai Ganesh
Registered: 2005-06-28
Posts: 47,758

### Re: *** Problems

mathsyperson,

It appears to me that if one wants to make progress in mathematics, one should study the masters and not the pupils. - Niels Henrik Abel.

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

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## #57 2006-03-18 16:42:20

Jai Ganesh
Registered: 2005-06-28
Posts: 47,758

### Re: *** Problems

***13. If the mth, nth and rth term of an Arithmetic Progression are in Geometric Progression, and m, n, and r are in Harmonic Progression, what is a/d of the Arithmetic Progression?

***14 What is the coefficient of

in
(1+x)(2+x)(3+x)(4+x)..............(99+x)(100+x)?

It appears to me that if one wants to make progress in mathematics, one should study the masters and not the pupils. - Niels Henrik Abel.

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

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## #58 2006-03-19 15:49:43

Jai Ganesh
Registered: 2005-06-28
Posts: 47,758

### Re: *** Problems

***15  The points (1,3) and (5,1) are the two opoosite vertices of a rectangle. The other two vertices lie on the line y=2x+c. Find c and the remaining vertices.

It appears to me that if one wants to make progress in mathematics, one should study the masters and not the pupils. - Niels Henrik Abel.

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

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## #59 2006-03-20 03:41:25

rm
Member
Registered: 2006-03-14
Posts: 14

### Re: *** Problems

***15
The diagonals of a parallelogram bisect each other. So y=2x+c must pass through middle of the opposite vertices - (3,2). On substituting, we get c = -4.
Let us say that vertices are (x,y) the angle between two lines from (x,y) to the other 2 vertices should be 90. Which is true if and only if m1 X m2 = -1. Using this and y=2x-4, we get the other vertices as (2,0) and (4,4)

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## #60 2006-03-20 05:46:13

Jai Ganesh
Registered: 2005-06-28
Posts: 47,758

### Re: *** Problems

It appears to me that if one wants to make progress in mathematics, one should study the masters and not the pupils. - Niels Henrik Abel.

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

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## #61 2006-03-20 15:41:32

Jai Ganesh
Registered: 2005-06-28
Posts: 47,758

### Re: *** Problems

***16 Find the incentre of a triangle whose vertices are (-4,6), (-2,-5), and (2,3).

***17 Given that x=cy+bz, y=az+cx, and z=bx+ay, where x,y,z≠0,
prove that a²+b²+c²+2abc=1.

***18 Prove that

is divisible by a-b.

***19 Prove that the complex numberx z1, z2 and the origin form an equilateral triangle only if z1²+z2²2z1z2=0

***20 The angles of a triangle are in the ratio 1:2:3. Show that the sides are in the ratio 1:√3:2.

***21 Prove that the maximum value of

is obtained when x=e.

It appears to me that if one wants to make progress in mathematics, one should study the masters and not the pupils. - Niels Henrik Abel.

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

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## #62 2006-03-21 15:24:45

rm
Member
Registered: 2006-03-14
Posts: 14

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## #63 2006-03-21 18:05:24

Jai Ganesh
Registered: 2005-06-28
Posts: 47,758

### Re: *** Problems

It appears to me that if one wants to make progress in mathematics, one should study the masters and not the pupils. - Niels Henrik Abel.

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

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## #64 2006-03-23 15:33:57

Jai Ganesh
Registered: 2005-06-28
Posts: 47,758

### Re: *** Problems

***22. In the Cartesian plane, four points have coordiantes (1,1), (4,2), (4,4),and (1,4). What is the are of the quadrilateral formed by joining the four points?

It appears to me that if one wants to make progress in mathematics, one should study the masters and not the pupils. - Niels Henrik Abel.

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

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## #65 2006-03-23 16:41:34

rm
Member
Registered: 2006-03-14
Posts: 14

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## #66 2006-03-23 17:24:18

Jai Ganesh
Registered: 2005-06-28
Posts: 47,758

### Re: *** Problems

Excellent, rm! You are correct!

It appears to me that if one wants to make progress in mathematics, one should study the masters and not the pupils. - Niels Henrik Abel.

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

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## #67 2006-03-24 00:33:56

Jai Ganesh
Registered: 2005-06-28
Posts: 47,758

### Re: *** Problems

***23  Find the sum of all numbers from 1 to 100 which are not divisible by 3 and 5.

It appears to me that if one wants to make progress in mathematics, one should study the masters and not the pupils. - Niels Henrik Abel.

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

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## #68 2006-03-24 01:56:34

Ikcelaks
Member
Registered: 2006-03-13
Posts: 8

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## #69 2006-03-24 03:36:31

Jai Ganesh
Registered: 2005-06-28
Posts: 47,758

### Re: *** Problems

Excellent, Ikcelaks!

It appears to me that if one wants to make progress in mathematics, one should study the masters and not the pupils. - Niels Henrik Abel.

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

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## #70 2006-03-31 07:50:48

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

### Re: *** Problems

***14
12582075

IPBLE:  Increasing Performance By Lowering Expectations.

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## #71 2006-04-14 17:57:08

Jai Ganesh
Registered: 2005-06-28
Posts: 47,758

### Re: *** Problems

OUTSTANDING, krassi_holmz!

This is how the problem is solved:-

The coefficient of

in the product would be the sum of the products of 1,2,3,...100 taking two at a time.

We know

where S would be the sum of the products of 1,2,3,4...100 taken two at a time.
Therefore, the required number

The summation formulas for n and n² have been used above.
Therefore, the coeficient of
would be
12582075.

It appears to me that if one wants to make progress in mathematics, one should study the masters and not the pupils. - Niels Henrik Abel.

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

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## #72 2006-04-16 16:54:44

Jai Ganesh
Registered: 2005-06-28
Posts: 47,758

### Re: *** Problems

***24. AB is the hypotenuse of a right-angled triangle ABC. If BC=x and AB+AC=y, what is the value of SinA?

***25. If

what is the value of tan(A)?

***26. If

where a+b+c≠0 and abc≠0, what is the value of
(a+b)(b+c)(c+a)?

It appears to me that if one wants to make progress in mathematics, one should study the masters and not the pupils. - Niels Henrik Abel.

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

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## #73 2006-04-17 16:19:17

Jai Ganesh
Registered: 2005-06-28
Posts: 47,758

### Re: *** Problems

***27 What is the remainder obtained when

is divided by 78?

***28 What is the remainder obtained when

is divided by 29?

It appears to me that if one wants to make progress in mathematics, one should study the masters and not the pupils. - Niels Henrik Abel.

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

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## #74 2006-04-23 04:36:13

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

### Re: *** Problems

26.
I think you've already gave that.

so:

Last edited by krassi_holmz (2006-04-23 04:44:06)

IPBLE:  Increasing Performance By Lowering Expectations.

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## #75 2006-04-23 04:51:57

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

### Re: *** Problems

27.

IPBLE:  Increasing Performance By Lowering Expectations.

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