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Variation

by k_suraj786 » Sat Apr 22, 2006 9:23 am
For a finite sequence of non zero numbers, the number of variations in sign is defined as the number of pairs of consecutive terms of the sequence for which the product of the two consecutive terms is negative. What is the number of variations in sign for the sequence 1, -3, 2, 5, -4, -6 ?

1. One
2. Two
3. Three
4. Four
5. Five
:roll:

This is getting really sick....?
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by chix475ntu » Sat Apr 22, 2006 9:29 am
3 ( 1 * -3 , -3 * 2, 5 * -4)

C
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by k_suraj786 » Sun Apr 23, 2006 8:02 am
Hey chix475ntu,

Thanks...!!!

:P
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answer is 3

by abby_g » Sat Sep 30, 2006 2:36 am
1,-3
-3,2
-5,4

hence C
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by BTGmoderatorRO » Sat Sep 23, 2017 10:06 pm
from the question, we have this (1, -3, 2, 5, -4, -6).
since we are concern with the variation in sign change, we will have the sequence in this form
1,-3 (+ve to -ve)
-3,2 (-ve to +ve)
-5,4 (-ve t +ve)

therefore, we have three variation.
hence,
option C is right
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by Brent@GMATPrepNow » Sun Sep 24, 2017 5:16 am
k_suraj786 wrote:For a finite sequence of non zero numbers, the number of variations in sign is defined as the number of pairs of consecutive terms of the sequence for which the product of the two consecutive terms is negative. What is the number of variations in sign for the sequence 1, -3, 2, 5, -4, -6 ?

1. One
2. Two
3. Three
4. Four
5. Five
We're asked to look at every pair of CONSECUTIVE numbers. If the product of that pair is NEGATIVE, this counts as one variation.

Let's examine the pairs of consecutive numbers:

1 and -3: product is negative
-3 and 2: product is negative
2 and 5: product is positive
5 and -4: product is negative
-4 and -6: product is positive

Since 3 pairs have negative products, the correct answer is C

Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
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Re: Variation

by Scott@TargetTestPrep » Sun Feb 02, 2020 12:44 pm
k_suraj786 wrote: ↑
Sat Apr 22, 2006 9:23 am
 For a finite sequence of non zero numbers, the number of variations in sign is defined as the number of pairs of consecutive terms of the sequence for which the product of the two consecutive terms is negative. What is the number of variations in sign for the sequence 1, -3, 2, 5, -4, -6 ?

1. One
2. Two
3. Three
4. Four
5. Five
:roll:

This is getting really sick....?
We are given the following sequence of numbers: 1, -3, 2, 5, -4, -6.

Every time a pair of consecutive terms produces a negative product, we have a “variation in sign.” We must determine the number of variations in sign in the sequence.

1 x (-3) = -3, so this is a variation in sign

(-3) x 2 = -6, so this is a variation in sign

(2) x (5) = 10, so this is NOT a variation in sign

5 x (-4) = -20, so this is a variation in sign

(-4) x (-6) = 24, so this is NOT a variation in sign

Thus, there is a total of 3 variations in sign.

Answer: C

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