herbertvl wrote:

Dear Everyone,

I just found out I won't be allowed to use a calculator during the quantative section of the GMAT. Mathematics is my weakest point in the test and this is quite a worrying fact for me. I'm working hard and doing some maths every day, but I was wondering if anyone has any tips/tricks and simple mathematical equations for me which I can apply.

To give you an example of my struggle, I have to calculate 460 . (0,85) for one of my questions. I have been doing these types of calculations with a calculator as far as I can remember and would have no clue how to solve it without one.

All help would be much appreciated,

Herbert van Litsenburg

Dear Herbert,

I'm happy to respond.

Here's a series of blogs I would recommend.

http://magoosh.com/gmat/2012/can-you-us ... -the-gmat/http://magoosh.com/gmat/2012/the-power- ... mat-quant/http://magoosh.com/gmat/2012/gmat-divis ... shortcuts/http://magoosh.com/gmat/2012/gmat-math- ... binations/http://magoosh.com/gmat/2012/doubling-a ... gmat-math/http://magoosh.com/gmat/2012/number-sense-for-the-gmat/You see, the GMAT is awfully unlikely to ask you to multiply, say, 460*(0.85) and find an exact value without a calculator. They could expect you to estimate the result --- for example, multiplying 460 by a number less than 1 will result in a product that is less than 460. Furthermore, 0.85 > 0.5, so clearly 460*(0.85) must be greater than 460*(0.5) = 230. It may be that, in whatever problem this appears, of the five answer choices, only one would be between 230 and 460, and this simple estimation would be enough to isolate the answer.

The GMAT could expect you to calculate, say, 250 * 84. For this, we can use the Doubling & Halving trick, discussed in the penultimate link above.

double of 250 is 500

half of 84 is 42,

so 250*84 = 500*42

repeat the process

half of 42 is 21

double of 500 is 1000

Therefore, 250*84 = 500*42 = 1000*21 = 21,000

My advice: between now and the GMAT,

[b]do not touch your calculator[/b]. Everyday, practice ordinary small number addition & subtraction & multiplication & division in your head. Too many people who aren't confident about math psyche themselves out so much that the wind up multiplying 4 times 6 on the calculator. Practice ordinary arithmetic every day, so at least these "muscles" are in shape by the time of the GMAT.

Let me know if you have any further questions

Mike

_________________

Mike McGarry

Magoosh Test Prep

Education is not the filling of a pail, but the lighting of a fire. — William Butler Yeats (1865 – 1939)