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In a certain sequence of 8 numbers, each number after the first is 1

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In a certain sequence of 8 numbers, each number after the first is 1  [#permalink]

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New post 15 Oct 2015, 21:56
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In a certain sequence of 8 numbers, each number after the first is 1 more than the previous number. If the first number is −5, how many of the numbers in the sequence are positive?

(A) None
(B) One
(C) Two
(D) Three
(E) Four


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Re: In a certain sequence of 8 numbers, each number after the first is 1  [#permalink]

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New post 15 Oct 2015, 23:55
Bunuel wrote:
In a certain sequence of 8 numbers, each number after the first is 1 more than the previous number. If the first number is −5, how many of the numbers in the sequence are positive?

(A) None
(B) One
(C) Two
(D) Three
(E) Four


Kudos for a correct solution.

-5,-4,-3,-2,-1,0,1,2 Answer (C)
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Re: In a certain sequence of 8 numbers, each number after the first is 1  [#permalink]

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New post 16 Oct 2015, 00:04
1
Bunuel wrote:
In a certain sequence of 8 numbers, each number after the first is 1 more than the previous number. If the first number is −5, how many of the numbers in the sequence are positive?

(A) None
(B) One
(C) Two
(D) Three
(E) Four


Kudos for a correct solution.


My Solution:

-5, -4, -3, -2, -1, 0, 1, 2

So only two numbers are positive (1 & 2) Answer C

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Re: In a certain sequence of 8 numbers, each number after the first is 1  [#permalink]

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New post 16 Oct 2015, 02:39
1
First term , a1 = -5
Common difference ,d =1
An= a1+(n-1)d
0 = -5 +(n-1)1 = -5 + n - 1 = n - 6
=> n = 6
Therefore, the number of terms which are positive is 8-6 =2

The list is -5 , -4 , -3 , -2 , -1 , 0 , 1 , 2
Number of terms which are positive = 2
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Re: In a certain sequence of 8 numbers, each number after the first is 1  [#permalink]

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New post 16 Oct 2015, 07:44
we have 0,1,2 as the non negative numbers; o is a positive number.
hence we have three positive numbers.
Answer is D

Thanks
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Re: In a certain sequence of 8 numbers, each number after the first is 1  [#permalink]

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New post 16 Oct 2015, 22:51
2
In a certain sequence of 8 numbers, each number after the first is 1 more than the previous number. If the first number is −5, how many of the numbers in the sequence are positive?

(A) None
(B) One
(C) Two
(D) Three
(E) Four

In GMAT Zero is considered as an integer which is neither positive nor negative.

Non - Negative ( zero to positive infinity )

Solution to the question :
-5,-4,-3,-2,-1,0 , 1,2

Hence ans is 2 ..option C
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Re: In a certain sequence of 8 numbers, each number after the first is 1  [#permalink]

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New post 30 Dec 2015, 23:47
Skywalker18 wrote:
First term , a1 = -5
Common difference ,d =1
An= a1+(n-1)d
0 = -5 +(n-1)1 = -5 + n - 1 = n - 6
=> n = 6
Therefore, the number of terms which are positive is 8-6 =2

The list is -5 , -4 , -3 , -2 , -1 , 0 , 1 , 2
Number of terms which are positive = 2

Hey Skywalker,

appreciate if you could explain the first part of your solution??
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Re: In a certain sequence of 8 numbers, each number after the first is 1  [#permalink]

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New post 31 Dec 2015, 00:09
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colorblind wrote:
Skywalker18 wrote:
First term , a1 = -5
Common difference ,d =1
An= a1+(n-1)d
0 = -5 +(n-1)1 = -5 + n - 1 = n - 6
=> n = 6
Therefore, the number of terms which are positive is 8-6 =2

The list is -5 , -4 , -3 , -2 , -1 , 0 , 1 , 2
Number of terms which are positive = 2

Hey Skywalker,

appreciate if you could explain the first part of your solution??


Hi colorblind ,
Please find the highlighted explanation in Blue .

First term , a1 = -5
Common difference ,d =1 (each number after the first is 1 more than the previous number )
The below is the formula for A.P
An= a1+(n-1)d
To find number of positive terms in the sequence we need to need number of integers equal to or less than 0.
So , i have calculated the position of 0 in the sequence . Zero is the 6th term in the sequence

0 = -5 +(n-1)1 = -5 + n - 1 = n - 6
=> n = 6
Therefore, the number of terms which are positive is 8-6 =2

Hope it helps !! :)
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Re: In a certain sequence of 8 numbers, each number after the first is 1  [#permalink]

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New post 31 Dec 2015, 08:13
Skywalker18 wrote:
First term , a1 = -5
Common difference ,d =1
An= a1+(n-1)d
0 = -5 +(n-1)1 = -5 + n - 1 = n - 6
=> n = 6
Therefore, the number of terms which are positive is 8-6 =2

The list is -5 , -4 , -3 , -2 , -1 , 0 , 1 , 2
Number of terms which are positive = 2


Hi Skywalker,

Thanks for the response, so:
An is the value of the nth term = 0
A1 is the first term = -5
n is the term number of interest =to find
d is the difference = 1

An = A1 + (n-1)d
0 = -5 + (n-1)*1
n = 6
So this formula comes handy for big set of numbers!

Great, I have never used this formula before. Thanks again!
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Re: In a certain sequence of 8 numbers, each number after the first is 1  [#permalink]

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New post 10 Jan 2016, 10:12
Hi Bunuel, thank you for your valuable posts, they are well explained and very complete! I have one question about 0 number in the GMAT: According to GMAT rules, 0 is considered as non negative and non positive, but in this example above, it is considered as positive number. Could you please exaplin me in which conditions can we consider it as positive?
Also, is it an even or odd number?
Thank you for your help!
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In a certain sequence of 8 numbers, each number after the first is 1  [#permalink]

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New post 10 Jan 2016, 10:39
KariLouise wrote:
Hi Bunuel, thank you for your valuable posts, they are well explained and very complete! I have one question about 0 number in the GMAT: According to GMAT rules, 0 is considered as non negative and non positive, but in this example above, it is considered as positive number. Could you please exaplin me in which conditions can we consider it as positive?
Also, is it an even or odd number?
Thank you for your help!


1. 0 is neither negative nor positive. In this question zero is not considered positive. Only digits 1 and 2 are considered positive.

2. Non-negative integers include "0"

2. 0 is an even number.
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Re: In a certain sequence of 8 numbers, each number after the first is 1  [#permalink]

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New post 10 Jan 2016, 10:55
KariLouise wrote:
Hi Bunuel, thank you for your valuable posts, they are well explained and very complete! I have one question about 0 number in the GMAT: According to GMAT rules, 0 is considered as non negative and non positive, but in this example above, it is considered as positive number. Could you please exaplin me in which conditions can we consider it as positive?
Also, is it an even or odd number?
Thank you for your help!


Where above is 0 considered as positive???

ZERO:

1. 0 is an integer.

2. 0 is an even integer. An even number is an integer that is "evenly divisible" by 2, i.e., divisible by 2 without a remainder and as zero is evenly divisible by 2 then it must be even.

3. 0 is neither positive nor negative integer (the only one of this kind).

4. 0 is divisible by EVERY integer except 0 itself.

Check more here: number-properties-tips-and-hints-174996.html
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PS: 1. Tough and Tricky questions; 2. Hard questions; 3. Hard questions part 2; 4. Standard deviation; 5. Tough Problem Solving Questions With Solutions; 6. Probability and Combinations Questions With Solutions; 7 Tough and tricky exponents and roots questions; 8 12 Easy Pieces (or not?); 9 Bakers' Dozen; 10 Algebra set. ,11 Mixed Questions, 12 Fresh Meat

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Re: In a certain sequence of 8 numbers, each number after the first is 1  [#permalink]

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