Find all School-related info fast with the new School-Specific MBA Forum

 It is currently 22 May 2015, 00:41

### GMAT Club Daily Prep

#### Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

# Events & Promotions

###### Events & Promotions in June
Open Detailed Calendar

# Some shortcuts of math

Author Message
TAGS:
Manager
Joined: 27 Jul 2011
Posts: 184
Followers: 0

Kudos [?]: 112 [1] , given: 103

Some shortcuts of math [#permalink]  17 Aug 2012, 17:45
1
KUDOS
This set is mixed one:(it is always good to approach formal way rather than to put some shortcut formulas....But why not give a try if it can save some time )

1. Area of a circle circumscribing equilateral triangle = $$\frac{pi}{3}a^2$$

2. Area of a circle inscribed in a equilateral triangle= $$\frac{pi}{12}a^2$$

3. Triangle formed by joining the mid points of a equilateral triangle will be half of perimeter and $$\frac{1}{4}area$$.

4.For a infinite GP series sum = $$\frac{a1}{(1-r)}$$ where a1 is the first term and r is multiplication factor

5. When Difference between compound interest and simple interest on a certain sum of money for 2 years at r% is
= $$\frac{(DIffX 100X100)}{(RateXRate)}$$

6. WHEN diff between CI and SI for 3 years at r% is given , then sum = $$\frac{Diff X100X100X100}{{(r^2)X(300+r)}}$$

7. If sum A becomes sum B in t1 years at compound rate of interest , then after t2 years the sum becomes

I am having a headache writing it properly - it is $${B^(t2/t1)} / { A^{(t2/t1)-1}}$$

8. Certain distance covered in xkm/hr and same distance y km/hr then avg speed = $$\frac{2xy}{x+y}$$

9. If two persons A and B start at the same time in opposite directions from two points and after passing each other they complete the journey
in a hrs and b hrs respectively . then A's speed : B's Speed = $$\sqrt{b} : \sqrt{a}$$

10.A man takes x hours to walk a certain place and ride back. However if he walks both ways he needs t hours more . Thus time taken
by him to ride both ways = $$(x-t)$$ hours.

I will post other tips if u like my post...(I mean If get few few kudos)...
_________________

If u can't jump the 700 wall , drill a big hole and cross it .. I can and I WILL DO IT ...need some encouragement and inspirations from U ALL

Senior Manager
Joined: 15 Sep 2009
Posts: 271
GMAT 1: 750 Q V
Followers: 9

Kudos [?]: 64 [0], given: 6

Re: Some shortcuts of math [#permalink]  27 Aug 2012, 08:01
Good initiative but honestly you are better off understanding concepts than memorizing "non-standard" abstruse formulae. Many high-performing quant students tend to rely on understanding quant through basic first principles. Moreover, higher level (700+) questions on the GMAT are so based on simple math and flexibility in thinking that sometimes memorized formulas can be a handicap, as they tend to restrict your thinking and frustrate you when you realize that you can't simply plug and chug.

That said, I understand different test takers use different strategies, so to each his own.

Cheers,
Der alte Fritz.
_________________

+1 Kudos me - I'm half Irish, half Prussian.

Senior Manager
Joined: 19 Apr 2009
Posts: 395
Location: San Francisco, California
Followers: 67

Kudos [?]: 261 [0], given: 4

Re: Some shortcuts of math [#permalink]  28 Aug 2012, 17:10
Personally, I agree with OldFritz, it is absolutely unnecessary to burden one's brain with abstruse formulas. For example, I am pretty certain that a very very small subsection of 99% scorers would know the expression for the Area of a circle circumscribing equilateral triangle. The GMAT doesn't really emphasize that. The only formula that I have ever used on the GMAT is the expression for the area of an equilateral triangle with side s, [sqrt(3)*s^2]/4. Other than that a problem solving mind set, along with the ability to think and approach a problem in multiple ways is probably more relevant for the GMAT.

Cheers,
Dabral
_________________

Free Video Explanations: OFFICIAL GUIDE FOR GMAT REVIEW 2015.
www.gmatquantum.com

Manager
Joined: 24 Jul 2011
Posts: 76
Location: India
Concentration: Strategy, General Management
GMAT 1: 670 Q49 V33
WE: Asset Management (Manufacturing)
Followers: 2

Kudos [?]: 82 [0], given: 5

Re: Some shortcuts of math [#permalink]  10 Sep 2012, 13:14
Though memorizing a few formula are helpful in quickly answering, however memorizing complicated formulas is sometimes difficult, specially geometry related formulas.

For your first two formulas, I would prefer to derive this value from properties of triangle ( Heitht = $$\sqrt{3}* a/ 2$$) , instead of memorizing them.
_________________

My mantra for cracking GMAT:
Everyone has inborn talent, however those who complement it with hard work we call them 'talented'.

+1 Kudos = Thank You Dear
Are you saying thank you?

Re: Some shortcuts of math   [#permalink] 10 Sep 2012, 13:14
Similar topics Replies Last post
Similar
Topics:
13 Must Have Scanned Handnote: Quantitative-GMAT-Math-Shortcuts 2 29 Nov 2012, 11:53
6 Some Out of the Box FORMULAS and SHORTCUTS 2 13 May 2011, 08:27
45 Math Formula and shortcuts 32 20 Apr 2009, 21:50
Some Math Questions from Gmatprep 3 12 Jun 2007, 17:57
some maths doubts... 1 10 Jul 2006, 07:45
Display posts from previous: Sort by