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# If js ­– k = m, what is s? (1) ms = k (2) j/m = 4

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Joined: 02 Sep 2009
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If js ­– k = m, what is s? (1) ms = k (2) j/m = 4  [#permalink]

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07 Sep 2017, 23:59
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45% (medium)

Question Stats:

63% (01:26) correct 37% (01:47) wrong based on 52 sessions

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If js ­– k = m, what is s?

(1) ms = k
(2) j/m = 4

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Re: If js ­– k = m, what is s? (1) ms = k (2) j/m = 4  [#permalink]

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08 Sep 2017, 00:20
Bunuel wrote:
If js ­– k = m, what is s?

(1) ms = k
(2) j/m = 4

(1) ms=k
no info abt j..not suff

(2) no inf abt k..not suff

on combining

(j/m)*s - (k/m) = 1
4s-s=1
3s = 1
s=1/3
Suff
C
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If js ­– k = m, what is s? (1) ms = k (2) j/m = 4  [#permalink]

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08 Sep 2017, 00:51
Rewriting the equation,
$$js = m + k$$
$$js - m = k$$
$$js^2 - ms = ks$$

1. $$ms = k$$
But only knowing value of ms is not enough(Insufficient)

2.$$\frac{j}{m} = 4$$
$$j = 4m$$
Knowing only the value of j is not enough (Insufficient)

We know that $$js^2 - ks = ms$$
On combining the information and substituting the values,
$$4m*s^2 - ms^2 = ms$$
$$3m*s^2 = ms$$
$$s = \frac{1}{3}$$ (Sufficient) (Option C)
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If js ­– k = m, what is s? (1) ms = k (2) j/m = 4  [#permalink]

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09 Sep 2017, 05:07
pushpitkc wrote:
Rewriting the equation,
$$js = m + k$$
$$js - m = k$$
$$js^2 - ms = ks$$

1. $$ms = k$$
But only knowing value of ms is not enough(Insufficient)

2.$$\frac{j}{m} = 4$$
$$j = 4m$$
Knowing only the value of j is not enough (Insufficient)

We know that $$js^2 - ks = ms$$
On combining the information and substituting the values,
$$4m*s^2 - ms^2 = ms$$
$$3m*s^2 = ms$$
$$s = \frac{1}{3}$$ (Sufficient) (Option C)

Why did you reduce 's'? are you sure that either s does not equal 0? We can reduce m because we from statement 2 that it can't be 0, otherwise, it would not be defined.

$$3*s^2 = s$$

$$3*s^2 - s = 0$$

$$s(3s - 1) = 0$$

s = 0 or s =1/3

so s could be 0 or 1/3........Insufficient
If js ­– k = m, what is s? (1) ms = k (2) j/m = 4   [#permalink] 09 Sep 2017, 05:07
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