which of the following is the best integer approximation of sqr(2)+sqr(5)+sqr(7)??
A) 6
B) 7
C) 8
D) 9
E) 10
Some trick to calculate sqr?
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the best integer approximation of
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Conquer Gmat
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Sqr(2) will be btwn 1 and 2
Sqr(5) will be btwn 2 and 3
Sqr(7) will be btwn 2 and 3
so min would be 5 and maximum would be 8. So our answer lies btwn 5 and 8.
Now out of the given ans choice it woould be 6,7,8
Now intelligent guessing needs to be done
Sqr(2) <1.5 as btwn 1 and 4 which are square numbers lies 2 and 3 and sqr (3) >1.5
and approximating more as there are 2 nos btwn 1and 4
take sqr(2) ~1.33
similarly
Sqr(5) <<2.5 and sqr (7) >2.5 as there are 4 nos 5,6,7,8 btwn 4 and 9 the two square nos.
and approximating more as there are 4 nos btwn 9and 4
take sqr(5) ~ 2.2
sqr(7) ~ 2. 6
Total = 1.33 + 2.2 + 2.6 = 6.13
Approximating take it as 6
Sqr(5) will be btwn 2 and 3
Sqr(7) will be btwn 2 and 3
so min would be 5 and maximum would be 8. So our answer lies btwn 5 and 8.
Now out of the given ans choice it woould be 6,7,8
Now intelligent guessing needs to be done
Sqr(2) <1.5 as btwn 1 and 4 which are square numbers lies 2 and 3 and sqr (3) >1.5
and approximating more as there are 2 nos btwn 1and 4
take sqr(2) ~1.33
similarly
Sqr(5) <<2.5 and sqr (7) >2.5 as there are 4 nos 5,6,7,8 btwn 4 and 9 the two square nos.
and approximating more as there are 4 nos btwn 9and 4
take sqr(5) ~ 2.2
sqr(7) ~ 2. 6
Total = 1.33 + 2.2 + 2.6 = 6.13
Approximating take it as 6
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lunarpower
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this is pretty much the idea. if you were to see something like this, you'd basically have to interpolate to figure out the approximate size of the roots.Conquer Gmat wrote:Sqr(2) will be btwn 1 and 2
Sqr(5) will be btwn 2 and 3
Sqr(7) will be btwn 2 and 3
so min would be 5 and maximum would be 8. So our answer lies btwn 5 and 8.
Now out of the given ans choice it woould be 6,7,8
Now intelligent guessing needs to be done
Sqr(2) <1.5 as btwn 1 and 4 which are square numbers lies 2 and 3 and sqr (3) >1.5
and approximating more as there are 2 nos btwn 1and 4
take sqr(2) ~1.33
similarly
Sqr(5) <<2.5 and sqr (7) >2.5 as there are 4 nos 5,6,7,8 btwn 4 and 9 the two square nos.
and approximating more as there are 4 nos btwn 9and 4
take sqr(5) ~ 2.2
sqr(7) ~ 2. 6
Total = 1.33 + 2.2 + 2.6 = 6.13
Approximating take it as 6
you don't really need to guess exact decimals; instead, you could just use "between 2 and 3 but closer to 2", "approx. halfway between 2 and 3", etc.
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i don't think this is a very gmat-like question, but it's not completely unreasonable.
moreover, this sort of skill at approximation can serve you very well on certain other types of problems, such as geometry problems (on which you can sometimes use a diagram to estimate the answer to a problem you have no idea how to solve).
Ron has been teaching various standardized tests for 20 years.
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Quand on se sent bien dans un vêtement, tout peut arriver. Un bon vêtement, c'est un passeport pour le bonheur.
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Pueden hacerle preguntas a Ron en castellano
Potete chiedere domande a Ron in italiano
On peut poser des questions à Ron en français
Voit esittää kysymyksiä Ron:lle myös suomeksi
--
Quand on se sent bien dans un vêtement, tout peut arriver. Un bon vêtement, c'est un passeport pour le bonheur.
Yves Saint-Laurent
--
Learn more about ron
