Hi All,
Faced the following questions in the GmatPrep software:
1) For all positive integers m, [m] = 3m when m is odd and [m] = (1/2)m when m is even. Which of the following is equivalent to [9] X [6] ?
a) [81]
b) [54]
c) [36]
d) [27]
e) [18]
OA is D
2) If n is a positive integer and the product of all integers from 1 to n, inclusive, is a multiple of 990, what is the least possible value of n?
a) 10
b) 11
c) 12
d) 13
e) 14
This is how I solved Q#2 - The prime factors for 990 are 2,3,5 and 11. Hence, a multiple of 990 should have the same set of prime factors and the least possible value of n in the product from 1 to n should be 11.Is my assumption right?? The OA is B.
3) Machines X and Y work at their respective constant rates. How many hours does it take machine Y, working alone to fill a production order of a certain size than it takes machine X, working alone?
(1) Machines X and Y, working together, fill a production order of this size in two-thirds the
time that machine X, working alone, does.
(2) Machine Y, working alone, fills a production order of this size in twice the time that
machine X, working alone, does.
This is how I solved Q#3:
Let x,y denote the number of hours taken by X and Y respectively to fill the production order. We need to find the value of y - x.
Taking Statement 1, we can conclude that (2/3)x = xy/(x+y). Since we have two unknown variables and one equation. NOT SUFFICIENT.
Taking Statement 2, it can be paraphrased as y = 2x and the value of y - x is x. But without the value of x we cannot find the difference. NOT SUFFICIENT
Taking (1) and (2), we get (2/3)x = xy/(x+y) and y = 2x.
Substituting (2) in (1), (2/3)x = 2x^2/3x. On simplifying, we get x = 1. And thus it takes 1 hour more for Y to fill the production order. SUFFICIENT. Thus, I selected option C.
But unfortunately, I was wrong and the OA is E. Can anyone tell me what was incorrect in my assumptions?
Faced the following questions in the GmatPrep software:
1) For all positive integers m, [m] = 3m when m is odd and [m] = (1/2)m when m is even. Which of the following is equivalent to [9] X [6] ?
a) [81]
b) [54]
c) [36]
d) [27]
e) [18]
OA is D
2) If n is a positive integer and the product of all integers from 1 to n, inclusive, is a multiple of 990, what is the least possible value of n?
a) 10
b) 11
c) 12
d) 13
e) 14
This is how I solved Q#2 - The prime factors for 990 are 2,3,5 and 11. Hence, a multiple of 990 should have the same set of prime factors and the least possible value of n in the product from 1 to n should be 11.Is my assumption right?? The OA is B.
3) Machines X and Y work at their respective constant rates. How many hours does it take machine Y, working alone to fill a production order of a certain size than it takes machine X, working alone?
(1) Machines X and Y, working together, fill a production order of this size in two-thirds the
time that machine X, working alone, does.
(2) Machine Y, working alone, fills a production order of this size in twice the time that
machine X, working alone, does.
This is how I solved Q#3:
Let x,y denote the number of hours taken by X and Y respectively to fill the production order. We need to find the value of y - x.
Taking Statement 1, we can conclude that (2/3)x = xy/(x+y). Since we have two unknown variables and one equation. NOT SUFFICIENT.
Taking Statement 2, it can be paraphrased as y = 2x and the value of y - x is x. But without the value of x we cannot find the difference. NOT SUFFICIENT
Taking (1) and (2), we get (2/3)x = xy/(x+y) and y = 2x.
Substituting (2) in (1), (2/3)x = 2x^2/3x. On simplifying, we get x = 1. And thus it takes 1 hour more for Y to fill the production order. SUFFICIENT. Thus, I selected option C.
But unfortunately, I was wrong and the OA is E. Can anyone tell me what was incorrect in my assumptions?
