Per today's daily GMAT Math Q:
A sum of money is to be divided among Ann, Bob and Chloe. First, Ann receives a $4 plus one half of what remains. Next, Bob receives $4 plus one third of what remains. Finally, Chloe receives the remaining $32. How much money did Bob receive?
(A) 20
(B) 22
(C) 24
(D) 26
(E) 52
Expert reply-
My solution is below. Note that we don't need to consider Ann's portion in the solution. We can just let K be the money remaining after Ann has received her portion and go from there.
Our equation will use the fact that, once we remove Bob's portion, we have $32 for Chloe.
So, we get K - Bob's $ = 32
The equation is K-4 - (K-4)/3 = 32
Solve for K (K=52) and then determine Bob's portion ($20).
The answer is, indeed, A
I don't understand why in the equation K - B= 32, if B= 4+(k-4)/3
when you plug in B for K-B shouldn't the negative carry through to all terms?
So why isn't it:
K - (4+(k-4)/3 =32
K - 4 - K+4/3 = 32
K - K+4/3 = 36
K-K =O which doesn't make sense?
Daily GMAT Math Q - explain
This topic has expert replies
GMAT/MBA Expert
- Brent@GMATPrepNow
- GMAT Instructor
- Posts: 16207
- Joined: Mon Dec 08, 2008 6:26 pm
- Location: Vancouver, BC
- Thanked: 5254 times
- Followed by:1268 members
- GMAT Score:770
Hey, I wrote that question (https://www.beatthegmat.com/tough-word-p ... 27218.html)ejager wrote: A sum of money is to be divided among Ann, Bob and Chloe. First, Ann receives a $4 plus one half of what remains. Next, Bob receives $4 plus one third of what remains. Finally, Chloe receives the remaining $32. How much money did Bob receive?
(A) 20
(B) 22
(C) 24
(D) 26
(E) 52
Expert reply-
My solution is below. Note that we don't need to consider Ann's portion in the solution. We can just let K be the money remaining after Ann has received her portion and go from there.
Our equation will use the fact that, once we remove Bob's portion, we have $32 for Chloe.
So, we get K - Bob's $ = 32
The equation is K-4 - (K-4)/3 = 32
Solve for K (K=52) and then determine Bob's portion ($20).
The answer is, indeed, A
I don't understand why in the equation K - B= 32, if B= 4+(k-4)/3
when you plug in B for K-B shouldn't the negative carry through to all terms?
So why isn't it:
K - (4+(k-4)/3 =32
K - 4 - K+4/3 = 32
K - K+4/3 = 36
K-K =O which doesn't make sense?
![Smile :-)](./images/smilies/smile.png)
The problem is above: K - 4 - K+4/3 = 32
It should be: K - 4 - (K-4)/3 = 32
The numerator k-4 is its own entity while part of the fraction.
Cheers,
Brent
The problem is above: K - 4 - K+4/3 = 32
It should be: K - 4 - (K-4)/3 = 32
The numerator k-4 is its own entity while part of the fraction.
In the second equation where does the second negative go if it doesn't affect (k-4)/3?
I don't understand why it shouldn't distribute out and then be
K - (K-4)/3 = 36
K - (K-4)= 108
K - K + 4 = 108
...? I know this is not the right answer but I don't get how to distribute the negative.
Thanks
It should be: K - 4 - (K-4)/3 = 32
The numerator k-4 is its own entity while part of the fraction.
In the second equation where does the second negative go if it doesn't affect (k-4)/3?
I don't understand why it shouldn't distribute out and then be
K - (K-4)/3 = 36
K - (K-4)= 108
K - K + 4 = 108
...? I know this is not the right answer but I don't get how to distribute the negative.
Thanks
- DavidG@VeritasPrep
- Legendary Member
- Posts: 2663
- Joined: Wed Jan 14, 2015 8:25 am
- Location: Boston, MA
- Thanked: 1153 times
- Followed by:128 members
- GMAT Score:770
This operation was where you went wrong. If you want to multiply both sides of the equation by 3, you'd go fromK - (K-4)/3 = 36
K - (K-4)= 108
K - (K-4)/3 = 36
to
3* [K - (K-4)/3] = 36 * 3
or
3K - (K - 4) = 108
GMAT/MBA Expert
- Ian Stewart
- GMAT Instructor
- Posts: 2621
- Joined: Mon Jun 02, 2008 3:17 am
- Location: Montreal
- Thanked: 1090 times
- Followed by:355 members
- GMAT Score:780
After we give Bob his $4, we know that he gets 1/3 of what's left, and Chloe gets 2/3 of what's left, so Chloe gets twice as much as Bob (not counting Bob's extra $4). Since Chloe got $32, Bob got $16. We need to add back Bob's additional $4, so the answer is $20.
For online GMAT math tutoring, or to buy my higher-level Quant books and problem sets, contact me at ianstewartgmat at gmail.com
ianstewartgmat.com
ianstewartgmat.com