, what is the value of z?
z --> +ve
y = 6.038 x 10^z
To find: value of "z"
Statement 1:
if z = 3 ==> 6038 out of range
if z = 4 ==> 60380
if z = 5 ==> 603800 out of range
SUFFICIENT
Statement 2:
y < 100000
y > 10000
Only Z=4 is satisfiable
SUFFICIENT
is it [spoiler]{D}[/spoiler]??
Exponents and powers
This topic has expert replies
Source: Beat The GMAT — Data Sufficiency |
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theCodeToGMAT
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[email protected]
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Hi mevicks,
On DS questions, I'm always curious about WHY the numbers/words are what they are. GMAT questions are written by humans to test other humans, so there's likely to be a pattern/formula/rule that is "built in" to the question (and there's usually more than 1).
Here, I'm curious abou the 6.038; THAT'S a real specific number. WHY did the author choose THAT number????
Before going to the Facts, I'm going to make some quick notes about the info that we're given:
If Z = 1, then Y = 60.38
If Z = 2, then Y = 603.8
If Z = 3, then Y = 6038
If Z = 4, then Y = 60,380
If Z = 5, then Y = 603,800
Fact 1 tells us that 6500 < Y < 65,000
The ONLY possibility is Z = 4
Fact 1 is SUFFICIENT
Fact 2 tells us that 10^4 < Y < 10^5
So 10,000 < Y < 100,000
The ONLY possibility is Z = 4
Fact 2 is SUFFICIENT
Final Answer: D
GMAT assassins aren't born, they're made,
Rich
On DS questions, I'm always curious about WHY the numbers/words are what they are. GMAT questions are written by humans to test other humans, so there's likely to be a pattern/formula/rule that is "built in" to the question (and there's usually more than 1).
Here, I'm curious abou the 6.038; THAT'S a real specific number. WHY did the author choose THAT number????
Before going to the Facts, I'm going to make some quick notes about the info that we're given:
If Z = 1, then Y = 60.38
If Z = 2, then Y = 603.8
If Z = 3, then Y = 6038
If Z = 4, then Y = 60,380
If Z = 5, then Y = 603,800
Fact 1 tells us that 6500 < Y < 65,000
The ONLY possibility is Z = 4
Fact 1 is SUFFICIENT
Fact 2 tells us that 10^4 < Y < 10^5
So 10,000 < Y < 100,000
The ONLY possibility is Z = 4
Fact 2 is SUFFICIENT
Final Answer: D
GMAT assassins aren't born, they're made,
Rich
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mevicks
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Totally agree with Rich on the pattern on the GMAT questions.
Saw it on a local test prep CAT and found it worthwhile. Shared this question for the very same reason -- the number is indeed a curious one
Saw it on a local test prep CAT and found it worthwhile. Shared this question for the very same reason -- the number is indeed a curious one
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ceilidh.erickson
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Just another note about patterns... whenever you see 10 taken to an exponent, like 10^x, they're testing place value (or you can call it Scientific Notation, powers of 10, orders of magnitude, etc).
When we want to know the value of z in 10^z, we really want to know: "6.038 will be raised to what power of 10," or in other words "where will the decimal go?"
1) If y is in a range that's one order of magnitude 6,500->65,000, there can only be one value in there that's 6.038 raised to some power of ten (some specific order of magnitude). Sufficient.
2) Again, y is in a range that's a different of one order of magnitude. Again, sufficient.
When we want to know the value of z in 10^z, we really want to know: "6.038 will be raised to what power of 10," or in other words "where will the decimal go?"
1) If y is in a range that's one order of magnitude 6,500->65,000, there can only be one value in there that's 6.038 raised to some power of ten (some specific order of magnitude). Sufficient.
2) Again, y is in a range that's a different of one order of magnitude. Again, sufficient.
Ceilidh Erickson
EdM in Mind, Brain, and Education
Harvard Graduate School of Education
EdM in Mind, Brain, and Education
Harvard Graduate School of Education
