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The product of two negative numbers is 160. If the lesser of the two

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The product of two negative numbers is 160. If the lesser of the two  [#permalink]

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New post 15 Jun 2016, 01:31
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The product of two negative numbers is 160. If the lesser of the two numbers is 4 less than twice the greater, what is the greater number?

A) -20
B) -16
C) -10
D) -8
E) -4

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Re: The product of two negative numbers is 160. If the lesser of the two  [#permalink]

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New post 19 Jul 2016, 22:53
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Bunuel wrote:
The product of two negative numbers is 160. If the lesser of the two numbers is 4 less than twice the greater, what is the greater number?

A) -20
B) -16
C) -10
D) -8
E) -4


Use the options. The options give you the greater number. Start from the middle option.

(C) - 10
Twice of -10 is -20 and 4 less is -24.
-24 * -10 = 240 (Not correct)

We need lower product (of 160) so try option (D).

(D) - 8
Twice of -8 is -16 and 4 less is -20.
-20 * -8 = 160
Correct

Answer (D)
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Re: The product of two negative numbers is 160. If the lesser of the two  [#permalink]

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New post 15 Jun 2016, 03:33
1
-a*-b =160 --1

-a=(-2b)-4 --2

substituting eq 2 in 1

(-2b-4)*-b=160
2b^2+4b-160=0
b^2+2b-80=o
b^2+10b-8b-80=0
b= -10,8
therefore -b =-8

substitute the value in eq 2
-a = -16-4= -20

therefore the larger number = -8
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Re: The product of two negative numbers is 160. If the lesser of the two  [#permalink]

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New post 15 Jun 2016, 04:27
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Bunuel wrote:
The product of two negative numbers is 160. If the lesser of the two numbers is 4 less than twice the greater, what is the greater number?

A) -20
B) -16
C) -10
D) -8
E) -4


let two numbers are a and b

a = 2b-4

Find value of b.

(2b-4)*b = 160
b*(b-2) = 80

b =-8 (Given that numbers are negative)

D is the answer.
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Re: The product of two negative numbers is 160. If the lesser of the two  [#permalink]

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New post 15 Jun 2016, 04:49
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1
Bunuel wrote:
The product of two negative numbers is 160. If the lesser of the two numbers is 4 less than twice the greater, what is the greater number?

A) -20
B) -16
C) -10
D) -8
E) -4


Consider two negative numbers as \(n_1\) and \(n_2\).

\(n_1 * n_2 = 160\)
\(n_2 = 2n_1 - 4\) ..... substitute this in above equation.

\(n_1 * (2n_1 - 4) = 160\)
\(2n_1^2 - 4n_2 - 160 = 0\)
\(n_1^2 - 2n_2 - 80 = 0\)
\((n_1 - 10) (n_1 +8) = 0\)
\(n_1 = 10\) and \(n_1 = -8\)

as mentioned in question, numbers are negative, we'll consider \(n_1 = -8\). substitute this in second equation.

\(n_2 = 2 * (-8) - 4\)
\(n_2 = -20\)

Hence the greater number is \(-8\).

\(Answer = D\)
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Re: The product of two negative numbers is 160. If the lesser of the two  [#permalink]

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New post 19 Jul 2016, 12:23
Confused about this..
The quadratic gives us two roots: (larger #)= -10 and (larger #)= +8
Curious why we didn't choose -10 since (although it is the smaller number between the roots, it is the only negative number.. and the question said that both numbers are negative).
Say we chose -10, then -10 x -16 also equals 160 and in this case -10 is in fact the larger number.

I'm sure I'm missing something since everyone got D.. can someone please tell me why D and not C?

Thanks in advance! :)
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Re: The product of two negative numbers is 160. If the lesser of the two  [#permalink]

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New post 19 Jul 2016, 12:28
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nk18967 wrote:
Confused about this..
The quadratic gives us two roots: (larger #)= -10 and (larger #)= +8
Curious why we didn't choose -10 since (although it is the smaller number between the roots, it is the only negative number.. and the question said that both numbers are negative).
Say we chose -10, then -10 x -16 also equals 160 and in this case -10 is in fact the larger number.

I'm sure I'm missing something since everyone got D.. can someone please tell me why D and not C?

Thanks in advance! :)


Hi! There,

We get the quadratic as x^2 -2x -80= 0

(x+8) (x-10)= 0

x can either be -8 or +10.

But because it is given that the numbers are -ve, we will choose -8.

Hope it is clear. :)
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Re: The product of two negative numbers is 160. If the lesser of the two  [#permalink]

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New post 19 Jul 2016, 13:04
Thanks Divyadisha!

Just realized what a silly mistake I made!

I had let the smaller # be (-a) and let the larger # be (-b)..
(-a) = 2(-b) - 4
(-a)(-b) = 160

So I solved it as:
[2(-b) - 4] [-b] = 160
[-2b - 4] [-b] = 160
2b^2 + 4b - 160 = 0
b^2 + 2b - 80 = 0
(b-8) (b+10)
So, b= 8 or b= -10

Here is where I forgot, that my number is actually (-b) :shock: !!!! That changes things because then my number can be either -(8) or -(-10)...which is +10..
SO... the Ans is obviously -8 since we need a -ve #!!

I hope I dont make these kind of mistakes when I'm taking the real test! Ugh..! :roll:

Divyadisha wrote:
nk18967 wrote:
Confused about this..
The quadratic gives us two roots: (larger #)= -10 and (larger #)= +8
Curious why we didn't choose -10 since (although it is the smaller number between the roots, it is the only negative number.. and the question said that both numbers are negative).
Say we chose -10, then -10 x -16 also equals 160 and in this case -10 is in fact the larger number.

I'm sure I'm missing something since everyone got D.. can someone please tell me why D and not C?

Thanks in advance! :)


Hi! There,

We get the quadratic as x^2 -2x -80= 0

(x+8) (x-10)= 0

x can either be -8 or +10.

But because it is given that the numbers are -ve, we will choose -8.

Hope it is clear. :)
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Re: The product of two negative numbers is 160. If the lesser of the two  [#permalink]

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New post 24 Sep 2016, 08:21
Two factors of 160 can be (1,160), (2,80), (4,40), (8, 20), (16,10), (32, 5). Considering the relation, lower = 2 higher -4, we can eliminate everything other than (8,20) and (16, 10) and the answer would be (-8, -20) i.e. -8
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Re: The product of two negative numbers is 160. If the lesser of the two  [#permalink]

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New post 06 Dec 2016, 08:28
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Bunuel wrote:
The product of two negative numbers is 160. If the lesser of the two numbers is 4 less than twice the greater, what is the greater number?

A) -20
B) -16
C) -10
D) -8
E) -4


We are given that the product of two negative numbers is 160 and that the lesser of the two numbers is 4 less than twice the greater.

We can let x = the larger number and y = the smaller number, and we can create the following equations:

(x)(y) = 160

AND

y = 2x - 4

Substituting (2x - 4) for y in the first equation yields:

x(2x - 4) = 160

2x^2 + 4x = 160

x^2 - 2x - 80 = 0

(x - 10)(x + 8) = 0

x = 10 or x = -8

Since x is negative, x = -8 and y = 2(-8) -4 = -20.

Thus, the greater number is -8.

Answer: D
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The product of two negative numbers is 160. If the lesser of the two  [#permalink]

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New post 06 Dec 2016, 12:41
Bunuel wrote:
The product of two negative numbers is 160. If the lesser of the two numbers is 4 less than twice the greater, what is the greater number?

A) -20
B) -16
C) -10
D) -8
E) -4


1. xy=160
2. x=2y-4
dividing 1. by 2.➡
y^2-2y-80=0
y=-8
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Re: The product of two negative numbers is 160. If the lesser of the two  [#permalink]

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New post 07 Dec 2016, 11:22
Bunuel wrote:
The product of two negative numbers is 160. If the lesser of the two numbers is 4 less than twice the greater, what is the greater number?

A) -20
B) -16
C) -10
D) -8
E) -4


\(-a*-b = 160\)

Let -a > -b

So, -b = -2a - 4

Or, -a( -2a - 4 ) = 160

Or, 2a^2 + 4a = 160

Or, 2a ( a + 2 ) = 16*10

Or, a = -8

So, b = -20

Thus, the greater number is (D) -8
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Re: The product of two negative numbers is 160. If the lesser of the two  [#permalink]

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New post 09 Oct 2017, 20:25
i think i did this a little different than most people above.

first, broke 160 down into pairs (below):

1, 160
2, 80
4, 40
5, 32
8, 20
10, 16

NOW, remember the question tells you that the LOWER # is 4 less than TWICE the greater? --> L=2S+4

Okay, let's see which #s (from list above) make sense...

1, 160
2, 80
4, 40
5, 32
8, 20
10, 16

Don't follow my logic? Well, let's set S=8. L=16+4. So, if S=8, L=20. Perfect fit.
> Don't fall for the trap: 10, 16. Here, if S=10, then L=24 [aka 2*10+4]

kudos please if you find this helpful :)
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Re: The product of two negative numbers is 160. If the lesser of the two  [#permalink]

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New post 09 Oct 2017, 22:15
Do the answer checking method,

-8*2 - 4 = -20

So greater number should be -8
Answer D
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Re: The product of two negative numbers is 160. If the lesser of the two  [#permalink]

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New post 15 Oct 2017, 08:47
1
Bunuel wrote:
The product of two negative numbers is 160. If the lesser of the two numbers is 4 less than twice the greater, what is the greater number?

A) -20
B) -16
C) -10
D) -8
E) -4



x = lesser
y = greater

(2y-4)(y) = 160
a , b , and c are too high values, so eliminate them

For e, (-12)(-4) =/ 160

For D, (-16-4)(-8) = (-20)(-8) = 160
Therefore, D)-8 is the answer
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Re: The product of two negative numbers is 160. If the lesser of the two  [#permalink]

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New post 18 Nov 2017, 04:26
ScottTargetTestPrep wrote:
Bunuel wrote:
The product of two negative numbers is 160. If the lesser of the two numbers is 4 less than twice the greater, what is the greater number?

A) -20
B) -16
C) -10
D) -8
E) -4


We are given that the product of two negative numbers is 160 and that the lesser of the two numbers is 4 less than twice the greater.

We can let x = the larger number and y = the smaller number, and we can create the following equations:

(x)(y) = 160

AND

y = 2x - 4

Substituting (2x - 4) for y in the first equation yields:

x(2x - 4) = 160

2x^2 + 4x = 160

x^2 - 2x - 80 = 0

(x - 10)(x + 8) = 0

x = 10 or x = -8

Since x is negative, x = -8 and y = 2(-8) -4 = -20.

Thus, the greater number is -8.

Answer: D


hello there :) it says product of two negative numbers- than why you write (x)(y) = 160 :? shouldn't it be (-x)(-y) = 160 Also how after this x^2 - 2x - 80 = 0 you get (x - 10)(x + 8) = 0 :?
I know formula B^2 - 4AC but couldn't use it properly, though I didn't divide whole equation by 2. Also after this (x - 10)(x + 8) = 0

you write that x = 10 or x = -8 ---> but how can x=10? if in brackets it is -10 and how can x = -8 if in brackets 8 is positive :?

thanks for taking time to explain and have a great day! :)
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Re: The product of two negative numbers is 160. If the lesser of the two  [#permalink]

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New post 11 Jan 2018, 15:48
Hi All,

This question can be solved by TESTing THE ANSWERS. We can also use a bit of logic to eliminate some of the work.

We're told that the product of 2 NEGATIVE numbers is 160. We're told that the LESSER of the two numbers is "4 less than twice" the GREATER value. We're asked for that greater value.

Before we do any work, it's worth noting that a "greater" negative number is the one that's CLOSER to 0. As an example...

-1 is GREATER than -1,000

Thus, the correct answer is almost certainly going to be C, D or E. Let's TEST Answer D....

Answer D: -8

IF the greater value is -8, then the lesser values is (2)(-8) - 4 = -16 - 4 = -20
Since (-8)(-20) does equal +160, then this is an exact match for what we're looking for - and this MUST be the answer!

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Re: The product of two negative numbers is 160. If the lesser of the two &nbs [#permalink] 11 Jan 2018, 15:48
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