Sally has a gold credit card with a certain spending limit, and a platinum card with twice the spending limit of the gold card. Currently, she has a balance on her gold card that is 1/3 of the spending limit on that card, and she has a balance on her platinum card that is 1/5 of the spending limit on that card. If Sally transfers the entire balance on her gold card to her platinum card, what portion of her limit on the platinum card will remain unspent?
11/30
29/60
17/30
19/30
11/15

For this question, please solve and explain me the answer. This question is frm a MGMAT and I don't understand the explanation completely.

let's say the gold credit card's limit is G and that of the platinum be P. we know:
1. P = 2G
Now, current balance on gold card = G/3 => P/6 [from 1..since in the end we want info on the platinum card, we should keep the variables that represent the Planitum card] and current balance on Plat. card = P/5.

"If Sally transfers the entire balance on her gold card to her platinum card" means P/6 + P/5 = 11/30 P.
This means that 11/30 of the platinum card is spent. "what portion of her limit on the platinum card will remain unspent" = 1-11/30=19/30 P.

you'll see that 11/30 will be an answer as lot of people will forget to answer the question asked!

makes sense?

Hi rohit,

since 11/30 is the balance left on the card, isnt that actually the amount unspent?

I found picking numbers works really well for this question.

Since we see that 1/3 and 1/5 are the fractions spent, assume the gold credit card has a limit of 15, and therefore the platinum card has a limit of 15*2=30.

Gold card balance: 1/3 * 15 = 5
Platinum card balance: 1/5 * 30 = 6
Sum of balances to transfer to platinum card: 5+6=11

Portion of platinum card spent = (Balance of platinum card) / (Spending limit of platinum card) = 11/30
Portion of platinum card unspent = 1 - 11/30 = (30-11)/30 = 19/30

nope.

you're thinking of debit cards, gift cards, etc., for which 'balance' refers to the amount left that you can spend.

this problem is about credit cards. on a credit card, a zero balance means that you haven't spent anything, and a numerical balance reflects the amount you've spent and now must pay off (not the amount that's left).

however, if you think it's the opposite, i have a few friends that wouldn't mind taking your credit cards and returning them to you with a nice high balance. xD

damn! Its a credit card! Thankq folks. No surprise I am making lot of silly mistakes....GMAT in 1 month :))

Good luck!