BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course

Redeem

Depreciation

Expert replies
by MBA.Aspirant » Sat Aug 06, 2011 7:09 pm
A piece of equipment cost a certain factory Rs. 600,000. If it depreciates in value, 15% the first year, 13.5% the next year, 12% the third year, and so on, what will be its value at the end of 10 years, all percentages applying to the original cost?

(a) 2,00,000
(b) 1,05,000
(c) 4,05,000
(d) 6,50,000
(e) 6,00,000
Join the discussion
Source: — Problem Solving |

by ajaykpat » Sat Aug 06, 2011 11:40 pm
IMO: E

BR,

ajp
Join the discussion

by GMATGuruNY » Sun Aug 07, 2011 12:11 am
MBA.Aspirant wrote:A piece of equipment cost a certain factory Rs. 600,000. If it depreciates in value, 15% the first year, 13.5% the next year, 12% the third year, and so on, what will be its value at the end of 10 years, all percentages applying to the original cost?

(a) 2,00,000
(b) 1,05,000
(c) 4,05,000
(d) 6,50,000
(e) 6,00,000
Depreciation the first year = (.15)*600,000 = 90,000.
Each year the amount of depreciation decreases by (.015)*600,000 = 9000.
Thus, after 9 years, the amount of depreciation in the 10th year = 90,000 - 9*9000 = 9000.
Since 90,000 is a multiple of 9000, and the amount of depreciation decreases by 9000 each year, the amounts of depreciation are the 10 consecutive multiples of 9000 between 90,000 and 9000, inclusive.

Given a set of evenly spaced integers:
Average = (biggest+smallest)/2
Sum = number * average

Thus, given the 10 multiples of 9000 between 90,000 and 9000, inclusive:
Average = (90,000 + 9000)/2 = 49,500.
Sum = 10 * 49,500 = 495,000.

Thus, the amount remaining = 600,000 - 495,000 = 105,000.

The correct answer is B.
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
Join the discussion

by prateek_guy2004 » Sun Aug 07, 2011 12:48 am
Well i did not know how to solve it...but i guessed it right(B)...now i knw...

Thanks GmatGuruNY
Join the discussion

by gmatboost » Sun Aug 07, 2011 10:15 pm
You could also apply the same reasoning directly to the percentages.

15% + 13.5% + ...
if you count out the 10 terms the last one is
... +1.5%

So, to sum a list of evenly spaced numbers:
sum = average * number of terms
average = (first + last)/2 = (15% + 1.5%) = 16.5%/2 = 8.25%
number of terms = 10
sum = 8.25% * 10 = 82.5% depreciation

So, 17.5% of the value remains. Multiply by 600,000.
Greg Michnikov, Founder of GMAT Boost

GMAT Boost offers 250+ challenging GMAT Math practice questions, each with a thorough video explanation, and 100+ GMAT Math video tips, each 90 seconds or less.
It's a total of 20+ hours of expert instruction for an introductory price of just $10.
View sample questions and tips without signing up, or sign up now for full access.


Also, check out the most useful GMAT Math blog on the internet here.
Join the discussion