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# What is the value of 1/k + 1/r ? (1) k + r = 20 (2) kr = 64

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Re: What is the value of 1/k + 1/r ? (1) k + r = 20 (2) kr = 64 [#permalink]
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Bunuel wrote:
What is the value of $$\frac{1}{k} + \frac{1}{r}$$ ?

(1) $$k + r = 20$$

(2) $$kr = 64$$

Asked: What is the value of $$\frac{1}{k} + \frac{1}{r}$$ ?
$$\frac{1}{k} + \frac{1}{r}$$
$$=\frac{k + r}{kr}$$

(1) $$k + r = 20$$
Since kr is unknown
NOT SUFFICIENT

(2) $$kr = 64$$
Since k + r is unknown
NOT SUFFICIENT

(1) + (2)
(1) $$k + r = 20$$
(2) $$kr = 64$$
$$\frac{1}{k} + \frac{1}{r}$$
$$=\frac{k + r}{kr}$$
$$=\frac{20}{64}$$
$$=\frac{5}{16}$$
SUFFICIENT

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Re: What is the value of 1/k + 1/r ? (1) k + r = 20 (2) kr = 64 [#permalink]
the only thing we need is the following rule: if we have the same or more equations than variables, we can find the variable's value.

in order to answer the question, we need the value of both variables.
1) and 2) are each, on their own, an equation with two variables = infinite solutions, insufficient!
Together - 2 equations with 2 variables ==> definitely solvable! sufficient!
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Re: What is the value of 1/k + 1/r ? (1) k + r = 20 (2) kr = 64 [#permalink]
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Re: What is the value of 1/k + 1/r ? (1) k + r = 20 (2) kr = 64 [#permalink]
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