Is a 10?

Question

Is a > 10?

(1) 1/a + 1/b = 1/c
(2) 1/a < 1/10

Bunuel · Answer

(1) 1/a +1/b=1/c. Clearly insufficient. (2) 1/a < 1/10 --> a>10 or a<0. Not sufficient. (1)+(2) Statement (1) is absolutely useless and (2) is not sufficient. Answer: E.

anilnandyala · Answer

(2) 1/a < 1/10 --> a>10 or a<0. Not sufficient. BUNUEL PLEASE EXPLAIN ME HOW a<0 thanks in advance

Bunuel · Answer

\frac{1}{10}>\frac{1}{a} --> \frac{1}{10}-\frac{1}{a}>0 --> \frac{a-10}{10a}>0 : Either both denominator and nominator are positive or both are negative: a>0 and a-10>0 , or a>10 --> a>10 ; a<0 and a-10<0 , or a<10 --> a<0 ; So, inequality \frac{1}{10}>\frac{1}{a} holds true for: a<0 and a>10 (even without the above solution you can spot that when a is negative then 1/a is negative, thus it's less than positive 1/10. Also when a>10, 1/10>1/a). Hope it's clear.

ajaysonu · Answer

You can't cross multiply as a can be -ve or +ve. The inequality will change accordingly.

bumpbot · Answer

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Is a > 10?

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