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Study Buddy Forum Moderator
Joined: 04 Sep 2016
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15 Jul 2018, 05:43
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15% (low)

Question Stats:

78% (01:40) correct 22% (02:33) wrong based on 110 sessions

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After her birthday, Fiona had D dollars in gift money. She spent 3/5 of this on an electric skateboard. The next day, she spent 1/3 of what was left on a movie passcard, and then finally put the last $80 in the bank. If she made no other purchases with that money, then what was the value of D? A.$240
B. $300 C.$320
D. $360 E.$480

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15 Jul 2018, 06:52
1
After her birthday, Fiona had D dollars in gift money. She spent 3/5 of this on an electric skateboard. The next day, she spent 1/3 of what was left on a movie passcard, and then finally put the last $80 in the bank. If she made no other purchases with that money, then what was the value of D? A.$240
B. $300 C.$320
D. $360 E.$480

OA: B

Initial amount =$$D$$
Amount remaining after buying Electric Skateboard =$$D- \frac{3D}{5}$$
Amount remaining after buying movie ticket =$$D- \frac{3D}{5} -\frac{1}{3}$$$$(D- \frac{3D}{5})=D*\frac{2}{5}*\frac{2}{3}$$
As per question stem,$$D*\frac{2}{5}*\frac{2}{3}=80$$
$$D=300$$
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15 Jul 2018, 06:59
Bismarck

Can you please comment on text in RED?

Initial amount =$$D$$
Amount remaining after buying Electric Skateboard =$$D- \frac{3D}{5}$$
OK, I simplified this to get $$\frac{2D}{5}$$

Amount remaining after buying movie ticket =$$D- \frac{3D}{5} -\frac{1}{3}$$$$(D- \frac{3D}{5})=D*\frac{2}{5}*\frac{2}{3}$$
I directly multiplied 1/3 *(2D/5) and then took 1-(2D/15) to equate to 80
Where did I go wrong?
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15 Jul 2018, 07:23
1
Can you please comment on text in RED?

Initial amount =$$D$$

Purchase 1
Amount remaining after buying Electric Skateboard =$$D- \frac{3D}{5}$$
OK, I simplified this to get $$\frac{2D}{5}$$
After buying Electric Skateboard,She has now $$\frac{2D}{5}$$ remaining with her, instead of $$D$$

Purchase 2
Amount remaining after buying movie ticket =$$D- \frac{3D}{5} -\frac{1}{3}$$$$(D- \frac{3D}{5})=D*\frac{2}{5}*\frac{2}{3}$$
I directly multiplied 1/3 *(2D/5) and then took 1-(2D/15) to equate to 80
Where did I go wrong?

Movie ticket price =$$\frac{1}{3} *(\frac{2D}{5})$$
Money remaining after Purchase 2 = Money remaining after Purchase 1 - Movie ticket price =$$\frac{2D}{5}$$ - $$\frac{1}{3} *(\frac{2D}{5})$$
Money remaining after Purchase 2$$=$$$$\frac{2D}{5}$$ $$-$$ $$\frac{1}{3} *(\frac{2D}{5})$$$$=80$$
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21 Jul 2018, 04:52
After her birthday, Fiona had D dollars in gift money. She spent 3/5 of this on an electric skateboard. The next day, she spent 1/3 of what was left on a movie passcard, and then finally put the last $80 in the bank. If she made no other purchases with that money, then what was the value of D? A.$240
B. $300 C.$320
D. $360 E.$480

Say D = $300 Expense on skate boards = 3/5 * 300 =$ 180

Balance amount = 300 - 180 = $120 Expense on smart card = 1/3 * 120 =$ 40

Total expense = 180 + 40 = $220 Amount left to put in the bank = 300 - 220 =$ 80 (perfect match)

(B)
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13 Aug 2018, 08:02
can somebody explain to me why this approach is incorrect:

I assume that Fiona has in total x dollars.

After the first purchase she is left with 5/3 of x and from this remaining amount she makes a second purchase which is 1/3 of the this amount.

Hence I calculated:

3/5x+1/3(3/5x)+80 = x
--> 9/15x + 3/15x+80 = x
--> 12/15x+80=x
--> 4/5x+80=x
-->80 = 1/5x
--> x = 400

Where is my logical flaw? From the post above it doesn't come clear to me.

Max
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06 Jan 2019, 09:01
Top Contributor
1
After her birthday, Fiona had D dollars in gift money. She spent 3/5 of this on an electric skateboard. The next day, she spent 1/3 of what was left on a movie passcard, and then finally put the last $80 in the bank. If she made no other purchases with that money, then what was the value of D? A.$240
B. $300 C.$320
D. $360 E.$480

One option is to WORK BACKWARDS

The next day, she spent 1/3 of what was left on a movie passcard, and then finally put the last $80 in the bank. If she spent 1/3 of her money on a movie passcard, then 2/3 of her money remained (which she put in the bank). This means 2/3 of her money =$80
We can also say that 1/3 of her money = $40 So, she spent$40 on a movie passcard and saved $80 In other words, at the beginning of that day, she had$120

After her birthday, Fiona had D dollars in gift money. She spent 3/5 of this on an electric skateboard.
If she spent 3/5 of her money (on a skateboard), then 2/5 of her money remained (to be spent on a movie passcard the following day).
In other words, 2/5 of D = $120 Or we can write: (2/5)D =$120
Multiply both sides by 5 to get: 2D = $600 Divide both sides by 2 to get: D =$300

Cheers,
Brent
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06 Jan 2019, 09:15
Top Contributor
After her birthday, Fiona had D dollars in gift money. She spent 3/5 of this on an electric skateboard. The next day, she spent 1/3 of what was left on a movie passcard, and then finally put the last $80 in the bank. If she made no other purchases with that money, then what was the value of D? A.$240
B. $300 C.$320
D. $360 E.$480

Another approach is to use algebra.

After her birthday, Fiona had D dollars in gift money. She spent 3/5 of this on an electric skateboard.
If Fiona SPENT 3/5 of D dollars, then 2/5 of D dollars REMAINED
In other words, the amount remaining at the end of the day = 2D/5 dollars

The next day, she spent 1/3 of what was left on a movie passcard, and then finally put the last $80 in the bank. If Fiona SPENT 1/3 of her remaining 2D/5 dollars, then she must have SAVED 2/3 of 2D/5 dollars 2/3 of 2D/5 = (2/3)(4D/5) = 4D/15 So, after spending 1/3 of her money that day, 4D/15 dollars remained (which she put in the bank) In other words, 4D/15 =$80

What was the value of D?
Take: 4D/15 = $80 Multiply both sides by 15 to get: 4D = 1200 Divide both sides by 4 to get: D =$300

Cheers,
Brent
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06 Jan 2019, 13:00
Hi All,

We're told that after her birthday, Fiona had D dollars in gift money. She spent 3/5 of this on an electric skateboard, then she spent 1/3 of what WAS LEFT on a movie passcard, and then finally put the last $80 in the bank. Assuming she made no other purchases with that money, we're asked for the value of D. This question can be solved in a number of different ways, including by TESTing THE ANSWERS. Based on the given Answers, it looks like Answer B would be the easiest to work with, so let's start there... Answer B:$300
IF.... D = $300.... Fiona spent (3/5)($300) = $180 on a skateboard, leaving her with$300 - $180 =$120
She then spent (1/3)($120) =$40 on a movie passcard, leaving her with $120 -$40 = $80 This is an exact match for what we were told, so this must be the answer! Final Answer: GMAT assassins aren't born, they're made, Rich _________________ 760+: Learn What GMAT Assassins Do to Score at the Highest Levels Contact Rich at: Rich.C@empowergmat.com # Rich Cohen Co-Founder & GMAT Assassin Special Offer: Save$75 + GMAT Club Tests Free
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