Target Test Prep 20% Off Flash Sale is on! Code: FLASH20

Redeem
Target Test Prep
5-Day Free Trial
5-day free, full-access trial TTP

Available with Beat the GMAT members only code

MORE DETAILS
Target Test Prep
Magoosh
Magoosh
Study with Magoosh GMAT prep

Available with Beat the GMAT members only code

MORE DETAILS
Magoosh

Tom saved $10,000 at a constant compound interest rate of r

This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
User avatar
Elite Legendary Member
Posts: 3991
Joined: Fri Jul 24, 2015 2:28 am
Location: Las Vegas, USA
Thanked: 19 times
Followed by:37 members

Tom saved $10,000 at a constant compound interest rate of r

by Max@Math Revolution » Wed Dec 05, 2018 11:19 pm

Timer

00:00

Your Answer

A

B

C

D

E

Global Stats

[Math Revolution GMAT math practice question]

Tom saved $10,000 at a constant compound interest rate of r percent annually. After 10 years, the balance is double the principal. What will be the balance 30 years after the deposit?

A. $30,000
B. $40,000
C. $50,000
D. $60,000
E. $80,000
Top
User avatar
GMAT Instructor
Posts: 15539
Joined: Tue May 25, 2010 12:04 pm
Location: New York, NY
Thanked: 13060 times
Followed by:1906 members
GMAT Score:790

by GMATGuruNY » Thu Dec 06, 2018 3:43 am
Max@Math Revolution wrote:[Math Revolution GMAT math practice question]

Tom saved $10,000 at a constant compound interest rate of r percent annually. After 10 years, the balance is double the principal. What will be the balance 30 years after the deposit?

A. $30,000
B. $40,000
C. $50,000
D. $60,000
E. $80,000

Original deposit: 10,000.
The balance doubles every 10 years.
After 10 years, we get:
2*10,000 = 20,000.
After 20 years, we get:
2*20,000 = 40,000.
After 30 years, we get:
2*40,000 = 80,000.

The correct answer is E.
Private tutor exclusively for the GMAT and GRE, with over 20 years of experience.
Followed here and elsewhere by over 1900 test-takers.
I have worked with students based in the US, Australia, Taiwan, China, Tajikistan, Kuwait, Saudi Arabia -- a long list of countries.
My students have been admitted to HBS, CBS, Tuck, Yale, Stern, Fuqua -- a long list of top programs.

As a tutor, I don't simply teach you how I would approach problems.
I unlock the best way for YOU to solve problems.

For more information, please email me (Mitch Hunt) at [email protected].
Student Review #1
Student Review #2
Student Review #3
Top
User avatar
Newbie | Next Rank: 10 Posts
Posts: 7
Joined: Mon Nov 19, 2018 8:18 am

by abhishekgoswami1234u » Thu Dec 06, 2018 8:12 am
The question says,the balance got doubled in 10 years of time.This means Balance after 10 years is 10,000*2= 20,000$ .Going by the same logic, and since in 20 years, the balance will be double of the balance in 10 years, which means 20,000*2= 40,000$. In another 10 years, that means, at the end of 30 years, the balance will again double up. The final balance will thus become 40,000*2= 80,000$.

Hence Answer
Top
User avatar
Elite Legendary Member
Posts: 3991
Joined: Fri Jul 24, 2015 2:28 am
Location: Las Vegas, USA
Thanked: 19 times
Followed by:37 members

by Max@Math Revolution » Sun Dec 09, 2018 5:49 pm
=>

After 10 years, we have 10,000(1+r)^10 = 20,000 or (1+r)^10 = 2.
So, after 30 years the balance is 10,000(1+r)^30 = 10,000((1+r)^10)^3= 10,000*2^3 =10,000*8 = 80,000.

Therefore, the answer is E.
Answer: E
Top
Post new topic Post Reply
• Page 1 of 1