Events & Promotions
|
|
GMAT Club Daily Prep
Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.
Customized
for You
Track
Your Progress
Practice
Pays
Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.
Nov 2007:30 AM PST
-08:30 AM PST
Learn what truly sets the UC Riverside MBA apart and how it helps in your professional growth
Nov 2211:00 AM IST
-01:00 PM IST
Do RC/MSR passages scare you? e-GMAT is conducting a masterclass to help you learn – Learn effective reading strategies Tackle difficult RC & MSR with confidence Excel in timed test environment- Nov 23
11:00 AM IST
-01:00 PM IST
Attend this free GMAT Algebra Webinar and learn how to master the most challenging Inequalities and Absolute Value problems with ease. 
Nov 2510:00 AM EST
-11:00 AM EST
Prefer video-based learning? The Target Test Prep OnDemand course is a one-of-a-kind video masterclass featuring 400 hours of lecture-style teaching by Scott Woodbury-Stewart, founder of Target Test Prep and one of the most accomplished GMAT instructors.
02 Oct 2025, 06:48
Kudos
Bookmarks
I can see we're working on this exponential growth problem - these bacteria doubling questions can definitely be tricky if you don't approach them systematically. Let me walk you through the core logic here.
Here's how to think about this step by step:
The key insight you need to grasp is that "doubles every 2 minutes" means we multiply the population by 2 after each 2-minute interval. So let's track this progression:
Step 1: Set up the doubling pattern
Starting point (Time = 0): 1,000 bacteria
Step 2: Track the growth systematically
After 2 minutes: \(1,000 \times 2 = 2,000\)
After 4 minutes: \(2,000 \times 2 = 4,000\)
After 6 minutes: \(4,000 \times 2 = 8,000\)
After 8 minutes: \(8,000 \times 2 = 16,000\)
After 10 minutes: \(16,000 \times 2 = 32,000\)
After 12 minutes: \(32,000 \times 2 = 64,000\)
After 14 minutes: \(64,000 \times 2 = 128,000\)
After 16 minutes: \(128,000 \times 2 = 256,000\)
After 18 minutes: \(256,000 \times 2 = 512,000\)
Step 3: Find when we exceed the target
Notice that at 16 minutes we have 256,000 bacteria (still below 500,000), but at 18 minutes we have 512,000 bacteria (which exceeds our target of 500,000).
Since the problem asks "approximately how many minutes," and we need to reach 500,000, we need 18 minutes to get there.
Answer: (E) 18
The critical thing to understand here is that growth happens at discrete 2-minute intervals - we can't have partial doublings, so we need to find the first time point where we meet or exceed the target.
For the complete systematic framework that works for all exponential growth problems, plus the time-saving techniques and common variations you'll see on the GMAT, you can check out the detailed solution on Neuron. You'll also find comprehensive explanations for similar official questions with step-by-step approaches that help you master these patterns consistently.
Here's how to think about this step by step:
The key insight you need to grasp is that "doubles every 2 minutes" means we multiply the population by 2 after each 2-minute interval. So let's track this progression:
Step 1: Set up the doubling pattern
Starting point (Time = 0): 1,000 bacteria
Step 2: Track the growth systematically
After 2 minutes: \(1,000 \times 2 = 2,000\)
After 4 minutes: \(2,000 \times 2 = 4,000\)
After 6 minutes: \(4,000 \times 2 = 8,000\)
After 8 minutes: \(8,000 \times 2 = 16,000\)
After 10 minutes: \(16,000 \times 2 = 32,000\)
After 12 minutes: \(32,000 \times 2 = 64,000\)
After 14 minutes: \(64,000 \times 2 = 128,000\)
After 16 minutes: \(128,000 \times 2 = 256,000\)
After 18 minutes: \(256,000 \times 2 = 512,000\)
Step 3: Find when we exceed the target
Notice that at 16 minutes we have 256,000 bacteria (still below 500,000), but at 18 minutes we have 512,000 bacteria (which exceeds our target of 500,000).
Since the problem asks "approximately how many minutes," and we need to reach 500,000, we need 18 minutes to get there.
Answer: (E) 18
The critical thing to understand here is that growth happens at discrete 2-minute intervals - we can't have partial doublings, so we need to find the first time point where we meet or exceed the target.
For the complete systematic framework that works for all exponential growth problems, plus the time-saving techniques and common variations you'll see on the GMAT, you can check out the detailed solution on Neuron. You'll also find comprehensive explanations for similar official questions with step-by-step approaches that help you master these patterns consistently.
