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Alice bought a certain number of 30 cent stamps, 35 cent stamps and 40

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Director
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Joined: 01 Oct 2017
Posts: 860
WE: Supply Chain Management (Energy and Utilities)
Alice bought a certain number of 30 cent stamps, 35 cent stamps and 40  [#permalink]

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14 Jul 2018, 03:04
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Difficulty:

75% (hard)

Question Stats:

51% (02:52) correct 49% (03:14) wrong based on 35 sessions

Alice bought a certain number of 30 cent stamps, 35 cent stamps and 40 cent stamps. She spent a total of $4.20 in buying these stamps. Did she buy more than 5 stamps of any of the three values? (1) The number of 35 cent stamps and 40 cent stamps that Alice bought are equal. (2) The number of 30 cent stamps and 40 cent stamps that Alice bought are equal. The number of 35 cent stamps that she bought was not more than the number of 40 cent stamps that she bought. Math Expert Joined: 02 Aug 2009 Posts: 6803 Alice bought a certain number of 30 cent stamps, 35 cent stamps and 40 [#permalink] Show Tags 14 Jul 2018, 05:00 1 PKN wrote: Alice bought a certain number of 30 cent stamps, 35 cent stamps and 40 cent stamps. She spent a total of$4.20 in buying these stamps. Did she buy more than 5 stamps of any of the three values?

(1) The number of 35 cent stamps and 40 cent stamps that Alice bought are equal.
(2) The number of 30 cent stamps and 40 cent stamps that Alice bought are equal. The number of 35 cent stamps that she bought was not more than the number of 40 cent stamps that she bought.

30a+35b+40c=420

(1) b=c
So 30a+75b=420
If b=2, 30a=420-150=270.....a=9 so >5
If b=4, 30a=420-300=120....a=4 and b=c=2 so none is greater than 5
Insufficient

(2) The number of 30 cent stamps and 40 cent stamps that Alice bought are equal. The number of 35 cent stamps that she bought was not more than the number of 40 cent stamps that she bought.

So a=c and $$b\leq{c}$$
So 30a+35b+40c=420......70a+35b=420.....you can divide entire equation by 35
2a+b=12.....
Max value of a is 5 and therefore max value of c is 5 and b cannot be greater than c
No combination of a,b,c greater than 5 is possible..
So sufficient

B
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1) Absolute modulus : http://gmatclub.com/forum/absolute-modulus-a-better-understanding-210849.html#p1622372
2)Combination of similar and dissimilar things : http://gmatclub.com/forum/topic215915.html
3) effects of arithmetic operations : https://gmatclub.com/forum/effects-of-arithmetic-operations-on-fractions-269413.html

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Re: Alice bought a certain number of 30 cent stamps, 35 cent stamps and 40  [#permalink]

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14 Jul 2018, 05:10
To find if Alice bought more than 5 stamps of any of the three values

Let x be the number of 30 stamps and x > 0
Let y be the number of 35 stamps and y > 0
Let z be the number of 40 stamps and z > 0

Alice spent a total of $4.20 in buying these stamps => 30x + 35y + 40z =$4.20 = 420 cents ------- (1)

Statement 1

The number of 35 cent stamps and 40 cent stamps that Alice bought are equal.

=> y = z

=> From equation 1, 30x + y(35 + 40) = 420

=> 30x + 75y = 420

Case 1)

x = 9, y = 2 satisfies the equation. So might have bought more than 5 30 cent stamps.

case 2)

x = 4, y = 4 satisfies the equation. So might have bought less than 5 30 cent stamps.

Since we don't get an unique answer, statement 1 is not sufficient.

Statement 2

The number of 30 cent stamps and 40 cent stamps that Alice bought are equal. The number of 35 cent stamps that she bought was not more than the number of 40 cent stamps that she bought.

=> x = z and y $$\leq$$ z = x

From equation 1, we get 30x + 40x + 35y = 420

=> 70x + 35y = 420 ---------- (2)

Since y $$\geq$$ 0 and y $$\leq$$ x lets start figuring out the minimum possible value for y

If y $$\geq$$0 and y is an integer lets start at y=1

=> 70x + 35 = 420

=> 70x = 385

=> x is not an integer which is false => y > 1

Lets see if y = 2

From equation 2, => 70x + 70 = 420

=> 70x = 350

=> x = 5

Since the minimum possible value for y is 2 and if y=2 => x = z = 5

=> x, z $$\leq$$ 5

Statement 2 is sufficient

Hence option B
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Director
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Re: Alice bought a certain number of 30 cent stamps, 35 cent stamps and 40  [#permalink]

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14 Jul 2018, 05:12
chetan2u wrote:
PKN wrote:
Alice bought a certain number of 30 cent stamps, 35 cent stamps and 40 cent stamps. She spent a total of $4.20 in buying these stamps. Did she buy more than 5 stamps of any of the three values? (1) The number of 35 cent stamps and 40 cent stamps that Alice bought are equal. (2) The number of 30 cent stamps and 40 cent stamps that Alice bought are equal. The number of 35 cent stamps that she bought was not more than the number of 40 cent stamps that she bought. 30a+35b+40c=420 (1) b=c So 30a+75b=420 If b=2, 30a=420-150=270.....a=9 so >5 If b=4, 30a=420-300=120....a=4 and b=c=2 so none is greater than 5 Insufficient (2) The number of 30 cent stamps and 40 cent stamps that Alice bought are equal. The number of 35 cent stamps that she bought was not more than the number of 40 cent stamps that she bought. So a=c and b>c So 30a+35b+40c=420......70a+35b=420.....you can divide entire equation by 35 2a+b=12..... Max value of a is 5 and therefore max value of c is 5 and b cannot be greater than c No combination of a,b,c greater than 5 is possible.. So sufficient B Hi chetan2u, Could you please correct me? I think it's $$b\leq{c}$$. _________________ Regards, PKN Rise above the storm, you will find the sunshine Manager Joined: 22 Jan 2014 Posts: 176 WE: Project Management (Computer Hardware) Re: Alice bought a certain number of 30 cent stamps, 35 cent stamps and 40 [#permalink] Show Tags 14 Jul 2018, 05:17 PKN wrote: Alice bought a certain number of 30 cent stamps, 35 cent stamps and 40 cent stamps. She spent a total of$4.20 in buying these stamps. Did she buy more than 5 stamps of any of the three values?

(1) The number of 35 cent stamps and 40 cent stamps that Alice bought are equal.
(2) The number of 30 cent stamps and 40 cent stamps that Alice bought are equal. The number of 35 cent stamps that she bought was not more than the number of 40 cent stamps that she bought.

PKN wrote:
Alice bought a certain number of 30 cent stamps, 35 cent stamps and 40 cent stamps. She spent a total of \$4.20 in buying these stamps. Did she buy more than 5 stamps of any of the three values?

(1) The number of 35 cent stamps and 40 cent stamps that Alice bought are equal.
(2) The number of 30 cent stamps and 40 cent stamps that Alice bought are equal. The number of 35 cent stamps that she bought was not more than the number of 40 cent stamps that she bought.

B.

let x,y,and z be # of 30,35,and 40 cent stamps respectively
so, 30x+35y+40z = 420

1) y=z
=> 30x+75k = 420
(k,x) = (2,9) & (4,4)
or (x,y,z) = (9,1,1) & (4,2,2)
insufficient.

2) x=z
=> 35y+70k = 420
(k,y) = (2,8) , (4,4) & (6,0)
or (x,y,z) = (1,8,1) , (2,4,2) & (3,0,3)
(1,8,1) is discarded since y =< z
so Alice did not purchase any value stamp in a quantity more than 5. sufficient.
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Re: Alice bought a certain number of 30 cent stamps, 35 cent stamps and 40 &nbs [#permalink] 14 Jul 2018, 05:17
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