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

You are not logged in.

- Topics: Active | Unanswered

Pages: **1**

**ganesh****Moderator**- Registered: 2005-06-28
- Posts: 13,895

Dec 6, 2008--->

#1. If

, then what is equal to?(1) 2(1+2m) (2)

(3) (4) 1 + m

Character is who you are when no one is looking.

Offline

**TooT****Member**- Registered: 2008-09-20
- Posts: 4

*Last edited by TooT (2008-12-06 00:00:14)*

TooT.

Offline

**ganesh****Moderator**- Registered: 2005-06-28
- Posts: 13,895

**Perfectly right, Toot! Keep it up!**

Character is who you are when no one is looking.

Offline

**ganesh****Moderator**- Registered: 2005-06-28
- Posts: 13,895

Dec 7, 2008 --->

#2. A boy multiplies 987 by a certain number and obtains 559981 as the result. If in the answers, both 9s are wrong and the other digits are correct, what is the correct value of the product?

(1) 553681 (2) 555181 (3) 555681 (4) 556581

*PS:- Marginally less difficult, being a Sunday *

Character is who you are when no one is looking.

Offline

**ganesh****Moderator**- Registered: 2005-06-28
- Posts: 13,895

Dec 7, 2008 --->

#2A. The sum of all possible two-digit numbers formed from three different one-digit natural numbers when divided by the sum of the original three numbers is equal to:

(1) 18 (2) 22 (3) 36 (4) None of these

Character is who you are when no one is looking.

Offline

**ganesh****Moderator**- Registered: 2005-06-28
- Posts: 13,895

Dec 10, 2008 --->

#3. If S be the sum, P the product and R the sum of reciprocals of n terms of a Geometric Progression, prove that

Character is who you are when no one is looking.

Offline

**Identity****Member**- Registered: 2007-04-18
- Posts: 934

Offline

**ganesh****Moderator**- Registered: 2005-06-28
- Posts: 13,895

**Very well done, Identity!!!**

Character is who you are when no one is looking.

Offline

**ganesh****Moderator**- Registered: 2005-06-28
- Posts: 13,895

Dec 11, 2008 --->

#4. Find the sum of all the numbers that can be formed with the digits 1,2,3,4,5 taken 4 at a time.

Character is who you are when no one is looking.

Offline

**ganesh****Moderator**- Registered: 2005-06-28
- Posts: 13,895

Dec 16, 2008 --->

#5. If

,then find the value of

.

Character is who you are when no one is looking.

Offline

**ganesh****Moderator**- Registered: 2005-06-28
- Posts: 13,895

Dec 28, 2008 --->

#6. The probability that a student is not a swimmer is

. Out of five students, find the probability that atleast 4 are swimmers.Character is who you are when no one is looking.

Offline

**ganesh****Moderator**- Registered: 2005-06-28
- Posts: 13,895

Dec 28, 2008 --->

#7. The cost of fuel in running an engine is proportional to the square of the speed and is #48 per hour for a speed of 16 kilometers per hour. Other expenses amount to $300 per hour. What is the most economical speed?

#8. Evaluate:

Character is who you are when no one is looking.

Offline

**Clint945****Member**- Registered: 2009-02-09
- Posts: 3

#8 this is probably totally wrong but:

(x^2/a)e^ax - (2x/a^2)e^ax + (2/a^3)e^ax + C

sorry for the rubbish way of typing it... wish i knew how to put in the proper formula font :S

*Last edited by Clint945 (2009-02-10 10:09:08)*

Why did the maths tree fall over?

It had no real roots!

Offline

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

I get the same answer as you, but with the third term added instead of subtracted.

The formula font is called LaTeX, and if you're interested there's a tutorial stickied at the top of the Help Me board.

Why did the vector cross the road?

It wanted to be normal.

Offline

**Clint945****Member**- Registered: 2009-02-09
- Posts: 3

oh yeah, it should be added, because its (x^2/a)e^ax - ((2x/a^2)e^ax - ∫ (2/a)e^ax) so its + the third term. sorry my bad, fixed it i always forget those little minus signs... *sigh*

*Last edited by Clint945 (2009-02-10 09:57:08)*

Why did the maths tree fall over?

It had no real roots!

Offline

**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 85,358

Hi ganesh;

My answer for #6

This is a bernoulli trial so:

**In mathematics, you don't understand things. You just get used to them.Of course that result can be rigorously obtained, but who cares?Combinatorics is Algebra and Algebra is Combinatorics.**

Offline

**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 85,358

Hi ganesh;

The answer to #4 is (3) 555681

*Last edited by bobbym (2009-04-28 07:14:40)*

**In mathematics, you don't understand things. You just get used to them.Of course that result can be rigorously obtained, but who cares?Combinatorics is Algebra and Algebra is Combinatorics.**

Offline

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

Dec 11:

24*15*1111 = 399960

Why did the vector cross the road?

It wanted to be normal.

Offline

**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 85,358

Hi ganesh;

Here is my answer to #10

Now multiply numerator and denominator by

*Last edited by bobbym (2009-04-28 07:15:22)*

**In mathematics, you don't understand things. You just get used to them.Of course that result can be rigorously obtained, but who cares?Combinatorics is Algebra and Algebra is Combinatorics.**

Offline

**belowaverage****Member**- Registered: 2009-04-20
- Posts: 2

hai ganesh,

my ans to ur question #10 is

or 2.828427125*Last edited by belowaverage (2009-04-20 15:41:39)*

Offline

Pages: **1**