GMAT Question of the Day - Daily to your Mailbox; hard ones only

 It is currently 16 Jan 2019, 10:27

### 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

we will pick new questions that match your level based on your Timer History

Track

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

## Events & Promotions

###### Events & Promotions in January
PrevNext
SuMoTuWeThFrSa
303112345
6789101112
13141516171819
20212223242526
272829303112
Open Detailed Calendar
• ### The winning strategy for a high GRE score

January 17, 2019

January 17, 2019

08:00 AM PST

09:00 AM PST

Learn the winning strategy for a high GRE score — what do people who reach a high score do differently? We're going to share insights, tips and strategies from data we've collected from over 50,000 students who used examPAL.
• ### Free GMAT Strategy Webinar

January 19, 2019

January 19, 2019

07:00 AM PST

09:00 AM PST

Aiming to score 760+? Attend this FREE session to learn how to Define your GMAT Strategy, Create your Study Plan and Master the Core Skills to excel on the GMAT.

# What is the units digit of 15^x + 22^y , where x and y are natural num

Author Message
TAGS:

### Hide Tags

Intern
Joined: 25 Jul 2018
Posts: 1
What is the units digit of 15^x + 22^y , where x and y are natural num  [#permalink]

### Show Tags

05 Jan 2019, 12:31
00:00

Difficulty:

(N/A)

Question Stats:

100% (00:37) correct 0% (00:00) wrong based on 7 sessions

### HideShow timer Statistics

What is the units digit of 15^x + 22^y , where x and y are natural numbers ?

(1) x = 6
(2) y = 18
Manager
Status: Manager
Joined: 27 Oct 2018
Posts: 97
Location: Malaysia
GPA: 3.67
WE: Pharmaceuticals (Health Care)
Re: What is the units digit of 15^x + 22^y , where x and y are natural num  [#permalink]

### Show Tags

05 Jan 2019, 13:04
Vshal wrote:
What is the units digit of 15^x + 22^y , where x and y are natural numbers ?

(1) x = 6
(2) y = 18

for statement 1: the value of x won't affect the result because the cyclic of '5' unit is always 5 --- "insufficient"

for statement 2: the value of y is required to find out the cyclic of '2' --- "Sufficient"
for details:
As y = 18 and the cyclic of '2' is 4 (2,4,8,6,...), the remainder of $$\frac{18}{4}$$ = 2 which shows that the unit digit of $$22^{18}$$ is 4
At the same time, the unit digit of 15^x is always 5 irrelevant of the value of x as long as x is a positive integer.
so the unit digit of $$15^x$$ + $$22^y$$ = 5 + 4 = 9

_________________

...Thanks for KUDOS

Intern
Joined: 16 Oct 2011
Posts: 46
GMAT 1: 620 Q37 V38
Re: What is the units digit of 15^x + 22^y , where x and y are natural num  [#permalink]

### Show Tags

05 Jan 2019, 20:29
Vshal wrote:
What is the units digit of 15^x + 22^y , where x and y are natural numbers ?

(1) x = 6
(2) y = 18

FYI, to my knowledge the GMAT does not use the term natural numbers. The GMAT will instead say "where x and y are positive integers"

(1) x=6 notice that any power of 5 gives us a units digit = 5, so this statement provides no useful info NS

(2) y = 18. The units digit for powers of 2 follows the following pattern: 2,4,8,6,2,4,8,6. Knowing y tells us which position in the sequence to take for the units digit of 22^y. The units digit of 15^x will always be 5 therefore 2 is suff. B
Manager
Joined: 28 Jul 2016
Posts: 206
Location: India
Concentration: Finance, Human Resources
GPA: 3.97
Re: What is the units digit of 15^x + 22^y , where x and y are natural num  [#permalink]

### Show Tags

05 Jan 2019, 20:51
simple question:
15^x + 22^y
i depends on value of y since the units digit of 5 remains same for any value of x.
Thus from statement 1: value of 22 ^x can me anything
looking at stmt 2 y =18.
18/4 = remainder 2
hence 2264 unit digit will be 4
thus 5+4 = 9

thus B is sufficient
_________________

Please give Kudos. Kudos encourage active discussions and help the community grow

Re: What is the units digit of 15^x + 22^y , where x and y are natural num &nbs [#permalink] 05 Jan 2019, 20:51
Display posts from previous: Sort by