Exponents & Roots

Expert replies

Previous Topic Next Topic

ramannjit: Senior | Next Rank: 100 Posts; Posts: 47; Joined: Sun May 09, 2010 7:21 am; Location: NewDelhi; Thanked: 1 times

by ramannjit » Tue Oct 05, 2010 3:00 am

If x, y , and z are integers, is x even?

(1) 10^x = (4^y)(5^z).
(2) 3^x+5 = 27^y+1

Ramannjit

Like this post

Source: Beat The GMAT — Data Sufficiency | Tue Oct 05, 2010 3:00 am

shovan85: Community Manager; Posts: 991; Joined: Thu Sep 23, 2010 6:19 amFollowed by: 24 members; Location: Bangalore, India; Thanked: 146 times

by shovan85 » Tue Oct 05, 2010 3:21 am

IMO A.

1: 10^x=(2^x)*(5^x)
(4^y)(5^z) = 2^2y * 5^z Thus (2^x)*(5^x) = 2^2y * 5^z => x = 2y and z.
If we see x=2y then x is even so sufficient.

2. After solving we get x+5 = 3y+3. Hence x can be odd or even depending on the value of y. so Not Suff.

Like this post

ramannjit: Senior | Next Rank: 100 Posts; Posts: 47; Joined: Sun May 09, 2010 7:21 am; Location: NewDelhi; Thanked: 1 times

by ramannjit » Tue Oct 05, 2010 3:29 am

shovan85 wrote:IMO A.

1: 10^x=(2^x)*(5^x)
(4^y)(5^z) = 2^2y * 5^z Thus (2^x)*(5^x) = 2^2y * 5^z => x = 2y and z.
If we see x=2y then x is even so sufficient.

2. After solving we get x+5 = 3y+3. Hence x can be odd or even depending on the value of y. so Not Suff.

Thanks yes OA is A.

My little mind is confused with (1), I came up with x=2y so it is even, what about x=z. Help me with this, why we will not consider relation between x and z, please.

Ramannjit

Like this post

mj78ind: Master | Next Rank: 500 Posts; Posts: 265; Joined: Mon Dec 28, 2009 9:45 pmFollowed by: 2 members; Thanked: 26 times; GMAT Score:760

by mj78ind » Tue Oct 05, 2010 4:35 am

ramannjit wrote:
shovan85 wrote:IMO A.

1: 10^x=(2^x)*(5^x)
(4^y)(5^z) = 2^2y * 5^z Thus (2^x)*(5^x) = 2^2y * 5^z => x = 2y and z.
If we see x=2y then x is even so sufficient.

2. After solving we get x+5 = 3y+3. Hence x can be odd or even depending on the value of y. so Not Suff.
Thanks yes OA is A.

My little mind is confused with (1), I came up with x=2y so it is even, what about x=z. Help me with this, why we will not consider relation between x and z, please.

x = z is besides the point, what are we going to do with it......since HAS to 2y hence both x and z HAVE to be even

Cheers

Call me 1 - (412) 897 6727 (US) or leave a msg on BTG for GMAT advise / questions.
If you like the solution, check out my debrief at and leave a comment:
https://www.beatthegmat.com/760-done-dea ... 66740.html

Like this post

Post new topic Post Reply

• Page 1 of 1

GMAT Course Reviews

560 reviews

1168 reviews

431 reviews

359 reviews

147 reviews

5/5

5 Star (560 Reviews)

"Target Test Prep is the closest to the official version of the GMAT exam, about 99% accuracy in terms of the quality and quantity of information. The course has excellently created singular sets of focused lessons and tests for every possible topic that one could come across in the official GMAT exam."

"The TTP course maximizes the efficiency of the time you spend studying. It will take time and effort but I could almost guarantee that if you complete the course exactly as it is laid out you will get an amazing score. They also have a very responsive team willing to help with any questions you might have."

"TTP has two things that I think no other test prep company offers: A teaching approach that reinforces understanding and an attitude that will give you the mental preparedness needed to succeed on the test. TTP gives you a deep understanding of the concept you need to know while teaching you how to think."

Write a Review