MGMAT EIV Guide 3, 4th ed P.195, #7

[bbukoye1]

Please explain how to solve by using direct algebra:
X% of Y% of Z is decreased by Y percent. What is the result?

Also what's the best way to determine when to pick a number versus solving with direct algebra?

thanks!

[gokul_nair1984]

Please explain how to solve by using direct algebra:
X% of Y% of Z is decreased by Y percent. What is the result?

X%=x/100
Y%=y/100

The word "of" means -You have to multiply

Therefore, X% of Y% of Z= (x/100)*(y/100)*(z)=(xyz)/10,000...

Let's call this bolded part A.

Furthermore, we have that, A is decreased by y/100 of A.

Let's first calculate y percent:(y/100)*(xyz/10,000)
=(x*y^2*z)/1000000

So value after decrease will be :(xyz)/10,000-(x*y^2*z)/1000000

Taking (xyz/10000) common, we get (xyz/10000)[1-(y/100)]------(B)

Picking numbers would be simpler:

Let x=100, y=100, z=100 (Since we are dealing with percents, 100 is best)

(100/100)*(100/100)*(100)=100

100% of 100= 100

100-100=0


Substitue x=100,y=100 and z=100 in (B) and you'll again arrive at 0.

Let me know whether this makes sense..

[bbukoye1]

got it!
thanks!

[tim]

:)