need your help ratio problem

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ronik74: Newbie | Next Rank: 10 Posts; Posts: 6; Joined: Thu May 03, 2012 4:23 am

need your help ratio problem

by ronik74 » Thu May 03, 2012 4:28 am

Hi there ,

please help me to understand this quastion soulution
:

Four brothers Adam, Bill, Charles and David together contributed certain amount of money and purchased a car. The contribution made by Adam is half that of the total contribution made by the other three brothers, contribution made by Bill is one-fourth of the total contribution made by the other three brothers and the contribution made by Charles is two-third of the total contribution made by the other three brothers. If the total price of the car is $9900, find the contribution made by David.

Answer Choices

A. $540

B. $580

C. $600

D. $660

E. $680

the right answer is D, please explain in details .

Tnx

Quote

Source: Beat The GMAT — Problem Solving | Thu May 03, 2012 4:28 am

kmittal82: Master | Next Rank: 500 Posts; Posts: 324; Joined: Mon Jul 05, 2010 6:44 am; Location: London; Thanked: 70 times; Followed by:3 members

by kmittal82 » Thu May 03, 2012 4:50 am

Let total (t) = a +b + c + d. We know that t = 9900, but lets keep it t for now

a = (b+c+d)/2 = (t-a)/2, so a = t/3

Similarly

b = (t-b)/4, so b = t/5

c = (t-c)x 2/3 = 2t/5

Putting it back in original equation, we have

d = t - (a + b + c)
= t - (t/3 + t/5 + 2t/5)
= 9900 - 3300 - 1980 - 3960
= 9900 - 9240
= 660

Quote

ronik74: Newbie | Next Rank: 10 Posts; Posts: 6; Joined: Thu May 03, 2012 4:23 am

by ronik74 » Thu May 03, 2012 5:08 am

Tnx for your reply,

please explain as most as you can, i missed something :

a = (b+c+d)/2 = (t-a)/2, so a = t/3

i dont get it how you get to a=t/3 ,