If a certain culture of bacteria increases by a constant factor of x every y minutes, how long will it take for the culture to increase to ten-thousand times its original size?
1. x=10^y
2.In two minutes, the culture will increase to one hundred times its original size.
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If a certain culture of bacteria increases by a constant
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RBBmba@2014
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GMATGuruNY
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Statement 1: x^(1/y) = 10.If a certain culture of bacteria increases by a constant factor of x every y minutes, how long will it take for the culture to increase to ten thousand times its original size.
1- x^(1/y)= 10
2 - In two minutes, the culture will increase to one hundred times its original size.
[x^(1/y)]^y = 10^y.
x = 10^y.
Since 10,000 = 10�, x=10,000 when y=4.
Thus, it will take y=4 minutes for the culture to increase by a factor of x=10,000.
SUFFICIENT.
Statement 2: In two minutes, the culture will increase to one-hundred times its original amount.
Thus, in 4 minutes, the culture will increase to 100*100 = 10,000 times its original size.
SUFFICIENT.
The correct answer is D.
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Hi bagdb@mba,
There's an alternative way to deal with Fact 1 (that I think that both Mitch and I are fans of):
Let's TEST values:
We're told that x is the constant factor of increase and y is the number of minutes per increase.
Fact 1 tells us that x = 10^y
If y = 1 minute
then x = 10 times bigger
Starting B bacteria
After 1 minute = 10B
After 2 minutes = 100B
After 3 minutes = 1,000B
After 4 minutes = 10,000B
If y = 2 minutes
then x = 100 times bigger
Starting B bacteria
After 2 minutes = 100B
After 4 minutes = 10,000B
You'll notice that the pattern leads to 4 minutes each time. Consistent = SUFFICIENT
GMAT assassins aren't born, they're made,
Rich
There's an alternative way to deal with Fact 1 (that I think that both Mitch and I are fans of):
Let's TEST values:
We're told that x is the constant factor of increase and y is the number of minutes per increase.
Fact 1 tells us that x = 10^y
If y = 1 minute
then x = 10 times bigger
Starting B bacteria
After 1 minute = 10B
After 2 minutes = 100B
After 3 minutes = 1,000B
After 4 minutes = 10,000B
If y = 2 minutes
then x = 100 times bigger
Starting B bacteria
After 2 minutes = 100B
After 4 minutes = 10,000B
You'll notice that the pattern leads to 4 minutes each time. Consistent = SUFFICIENT
GMAT assassins aren't born, they're made,
Rich
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royrijit1
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Dear Experts/Moderators,
I am comparatively weak in such concepts(relative increases in populations). Request you to please post few similar questions solving which I can master this topic.
Thanks a lot in advance!
-RR1
I am comparatively weak in such concepts(relative increases in populations). Request you to please post few similar questions solving which I can master this topic.
Thanks a lot in advance!
-RR1
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Hi royrijit1,
This question involves a 'geometric progression', which is relatively rare on Test Day (you probably won't see it at all). You WILL see questions that involve sequences, percentage increases/decreases and percentage change though (and you've probably already seen these concepts in the materials that you're using).
How long have you been studying?
What practice materials have you been using?
GMAT assassins aren't born, they're made,
Rich
This question involves a 'geometric progression', which is relatively rare on Test Day (you probably won't see it at all). You WILL see questions that involve sequences, percentage increases/decreases and percentage change though (and you've probably already seen these concepts in the materials that you're using).
How long have you been studying?
What practice materials have you been using?
GMAT assassins aren't born, they're made,
Rich
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Max@Math Revolution
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Forget conventional ways of solving math questions. In DS, Variable approach is the easiest and quickest way to find the answer without actually solving the problem. Remember equal number of variables and equations ensures a solution.
If a certain culture of bacteria increases by a constant factor of x every y minutes, how long will it take for the culture to increase to ten-thousand times its original size?
1. x=10^y
2.In two minutes, the culture will increase to one hundred times its original size.
Since there are 2 variables (x,y) in the original condition, we need 2 equations to match the number of variables and equations. We have 1 each in 1) and 2), therefore C is likely the answer.
Using both 1) & 2) together,
In case of 1), x=10^6. Since the value is multiplied by 10^6 every 6 minute, the answer is 6 minute.
In case of 2), since the value is multiplied by 100 every 2 minute, it's 10,000times for 4 minutes and 1,000,000 for 6 minutes. Since 1) = 2), The answer is D.
If you know our own innovative logics to find the answer, you don't need to actually solve the problem.
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If a certain culture of bacteria increases by a constant factor of x every y minutes, how long will it take for the culture to increase to ten-thousand times its original size?
1. x=10^y
2.In two minutes, the culture will increase to one hundred times its original size.
Since there are 2 variables (x,y) in the original condition, we need 2 equations to match the number of variables and equations. We have 1 each in 1) and 2), therefore C is likely the answer.
Using both 1) & 2) together,
In case of 1), x=10^6. Since the value is multiplied by 10^6 every 6 minute, the answer is 6 minute.
In case of 2), since the value is multiplied by 100 every 2 minute, it's 10,000times for 4 minutes and 1,000,000 for 6 minutes. Since 1) = 2), The answer is D.
If you know our own innovative logics to find the answer, you don't need to actually solve the problem.
www.mathrevolution.com
- The one-and-only World's First Variable Approach for DS and IVY Approach for PS that allow anyone to easily solve GMAT math questions.
- The easy-to-use solutions. Math skills are totally irrelevant. Forget conventional ways of solving math questions.
- The most effective time management for GMAT math to date allowing you to solve 37 questions with 10 minutes to spare
- Hitting a score of 45 is very easy and points and 49-51 is also doable.
- Unlimited Access to over 120 free video lessons at https://www.mathrevolution.com/gmat/lesson
- Our advertising video at https://www.youtube.com/watch?v=R_Fki3_2vO8
