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lsv

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1/ Joanna bought only $0.15 stamps and $0.29 stamps. How many $0.15 stamps did she buy?

(1) She bought $4.40 worth of stamps.

(2) She bought an equal number of $0.15 stamps and $0.29 stamps.

 

2/ The ratio of the number of red cars in a certain parking lot to the number of black cars is 3 to 8. If there are 72 black cars in the lot, how many red cars are there in the lot?

11

15

24

27

32

 

3/ If the average (arithmetic mean) of x, y, and 20 is 10 greater than the average of x, y, 20, and 30, what is the average of x and y?

 

4/ In the xy-plane, line l and line k intersect at the point (16/5, 12/5). What is the slope of line l?

(1) The product of the slopes of line l and line k is –1.

(2) Line k passes through the origin.

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Question 1:

The problem can be expressed in an equation as following:

0.15 X + 0.29 Y = Z, where X and Y are the prices of the stamps, and Z the total amount of the purchase.

 

(1) says that Z = $4.40 It doesn't allow to solve the equation by itself

--> INSUFF

 

(2) says that X=Y so we can replace Y by X. We still have two unknown variables (X and Z)

--> INSUFF

 

(1) and (2) : replacing all variables by the given information, only X remains

--> SUFFICIENT

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1) A

If .15x + .29y = 4.40.

The only combination I got to work was y=10 and x=10. Since we are working with a 9 in the hundreths digit, and the total sum has a 0, y has to be a multiple of 5. It can only be 0, 5, 10, 15. Anything else would be over 4.40. The only one that can work is 10. Forcing x=10.

 

2) D

R/B = 3/8 R = (3/8)B --> R = (3/8)*72 = 27

 

3) 115

x+y+20 / 3 = x+y+20+30/4 + 10 -> solve for x+y = 230

x+y / 2 = 115

 

4) C

Each individual statement was insuff, but together you can figure out slope of k = 3/4. Then solve for (3/4)*I = -1. I = -4/3.

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1) A

If .15x + .29y = 4.40.

The only combination I got to work was y=10 and x=10. Since we are working with a 9 in the hundreths digit, and the total sum has a 0, y has to be a multiple of 5. It can only be 0, 5, 10, 15. Anything else would be over 4.40. The only one that can work is 10. Forcing x=10.

 

3) 115

x+y+20 / 3 = x+y+20+30/4 + 10 -> solve for x+y = 230

x+y / 2 = 115

 

4) C

Each individual statement was insuff, but together you can figure out slope of k = 3/4. Then solve for (3/4)*I = -1. I = -4/3.

 

Qn 1/ Other than random trial and error, can anyone propose a diff method ? Thanks.. I'd like to know if there are any alternative ways to solve..

 

Qn 3/

95 - I'd think.

 

Qn 4/

Stmt 1) m1*m2 =-1 Insuff

Stmt 2) Let us write the equation of like k:

y=mx+c => 12/5 = (16/5)m+c. The line passes through the origin. So, c = 0. m = 3/4.

So, only B should be enough, isnt it ?? Pl clarify..

 

Thanks..

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q1: I think is D.

in both case a try and error technic should work as an explanation. Reasoning about number of variable and number of equation, I agree with Fabrisco however in both cases (1 and 2) there are only one combination possible.

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Qn 1/ Other than random trial and error, can anyone propose a diff method ? Thanks.. I'd like to know if there are any alternative ways to solve..

 

Qn 3/

95 - I'd think.

 

Qn 4/

Stmt 1) m1*m2 =-1 Insuff

Stmt 2) Let us write the equation of like k:

y=mx+c => 12/5 = (16/5)m+c. The line passes through the origin. So, c = 0. m = 3/4.

So, only B should be enough, isnt it ?? Pl clarify..

 

Thanks..

 

Qn 1:

I agree with cippo that you can solve for how many stamps using B with trial and error.

 

Qn3:

Math error on my part lsv is correct. a+b = 190....so avg = 95

 

Qn4:

The question asks for the slope of I, not just the slope of k. I think you need both a and b to solve this.

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1. Try and error seems the only approach but the question is how do you know instantly that a (10,10) choise will work. Any Mathematic approach? Or else most guys (including myself) would have settled with a C.

 

2. R/B = 3/8 , so if B = 72 => R is (72/8)*3 which is 27

3. yeah a 95 ie (190/2)

4. It should be a C not B because we need the slope of L not K.

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Qn 1:

I agree with cippo that you can solve for how many stamps using B with trial and error.

 

Qn3:

Math error on my part lsv is correct. a+b = 190....so avg = 95

 

Qn4:

The question asks for the slope of I, not just the slope of k. I think you need both a and b to solve this.

 

u guys be careful. when u say u can solve with information provided in statement B using trial and error, I think you are bringing information from A.

Ignore statement A and look at the problem

 

------------------------------------------------------------------

Joanna bought only $0.15 stamps and $0.29 stamps. How many $0.15 stamps did she buy

 

She bought an equal number of $0.15 stamps and $0.29 stamps

------------------------------------------------------------------

what trial and error you are talking about????

 

from statement A

.15x+.29y=4.40

the above equation is in the form of ax+by = (a+b)*m ".15x+.29y=(.15+.29)*10"

so as a rule, if a constant in a linear equation is a mutiple of sum of the coefficients of x & y, then x and y have to be equal.

So the answer is A

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Q1:

 

Hi cippo, andes,

 

Though arrived at answer A, based on trial and error approach, the second option (B) clearly says the stamps bought were equal in number. so, how could you ignore B as if that was not given.

If statement (B) reads something else, then I will say the answer is A, but for this question the answer should be C.

ISV, could you post the OA?

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Q1:

 

Hi cippo, andes,

 

Though arrived at answer A, based on trial and error approach, the second option (B) clearly says the stamps bought were equal in number. so, how could you ignore B as if that was not given.

If statement (B) reads something else, then I will say the answer is A, but for this question the answer should be C.

ISV, could you post the OA?

It is A.

 

Can someone clarify qn 4 ?

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Qn 1/ Other than random trial and error, can anyone propose a diff method ? Thanks.. I'd like to know if there are any alternative ways to solve..

 

Qn 3/

95 - I'd think.

 

Qn 4/

Stmt 1) m1*m2 =-1 Insuff

Stmt 2) Let us write the equation of like k:

y=mx+c => 12/5 = (16/5)m+c. The line passes through the origin. So, c = 0. m = 3/4.

So, only B should be enough, isnt it ? Pl clarify..

 

Thanks..

with statement B you got the slope of k, but the question asks for the slope of l

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  • 2 weeks later...
On question 2, isn't it saying there are 8 black cars for every three red cars, not three red cars out of eight total cars, so the ratio should be 3/11, not 3/8 (because that's saying there's only 5 black cars for every three red cars) . . . but then the problem isn't solvable.
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1) A

If .15x + .29y = 4.40.

The only combination I got to work was y=10 and x=10. Since we are working with a 9 in the hundreths digit, and the total sum has a 0, y has to be a multiple of 5. It can only be 0, 5, 10, 15. Anything else would be over 4.40. The only one that can work is 10. Forcing x=10.

 

2) D

R/B = 3/8 R = (3/8)B --> R = (3/8)*72 = 27

 

3) 115

x+y+20 / 3 = x+y+20+30/4 + 10 -> solve for x+y = 230

x+y / 2 = 115

 

4) C

Each individual statement was insuff, but together you can figure out slope of k = 3/4. Then solve for (3/4)*I = -1. I = -4/3.

 

agree but I get sol for 3 as 95

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It is A.

 

Can someone clarify qn 4 ?

 

eqn of line = y=mx+c

 

A) with eqn we know prod of slopes is -1 but we have neither slopes hence not suff

 

b) says one line passes through origin (0,0)

 

subs in y=mx+c

we get c=0

but no m so in suff

 

when we take both and since we know other point is (12/5,16/5)

 

we can derive the new eqn which is y=mx+C but c is 0

 

hence y=mx

subs values

12/5=m(16/5)

m=3/4

we know the prod of the 2 slopes in -1

hence the other slope must be -4/3

 

Hence C

 

HTH

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  • 1 year later...
  • 4 months later...

IMO:

1. The answer will be C. With both the statements it becomes a matter of solving an equation, which we can do.

Many people are talking about trial and error. Lets consider just the statement 1. it says;

0.15*x + 0.29*y = 4.4

x is number of $0.15 stamps and y is number of $0.29stamps. Well there can be n number of solutions for this. How do we know when to stop. I dont think DS is suppose to be solved like that.

Hence answer should be C

 

2. answer is 27. Red/Black = 3/8 hence red = 27 (when black is 72)

 

3. Answer is 95

Solve the equation for x+y:

(x+y+20)/3 = (x+y+20+30)/4 + 10

x+y = 190

Hence average = 95

 

4. Answer should be C.

Just by knowing product of slopes and the intersection point we can not determine any information.

Just by knowing K passes through origin, we can only determine equation for k but nothing about line l.

But if we put that together. From two we can get equation & slope for line k. As product of slopes is given by statement 1 we can fine slope for l.

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