Last visit was: 21 Apr 2026, 23:51 It is currently 21 Apr 2026, 23:51
Close
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
Your Progress

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
Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.
Close
Request Expert Reply
Confirm Cancel
User avatar
HiteshPunjabi
Joined: 27 Aug 2012
Last visit: 10 Mar 2014
Posts: 11
Own Kudos:
76
 [10]
Given Kudos: 8
Schools: Anderson '15
Schools: Anderson '15
Posts: 11
Kudos: 76
 [10]
Kudos
Add Kudos
10
Bookmarks
Bookmark this Post
Most Helpful Reply
User avatar
Bunuel
User avatar
Math Expert
Joined: 02 Sep 2009
Last visit: 21 Apr 2026
Posts: 109,740
Own Kudos:
810,510
 [1]
Given Kudos: 105,816
Products:
Expert
Expert reply
Active GMAT Club Expert! Tag them with @ followed by their username for a faster response.
Posts: 109,740
Kudos: 810,510
 [1]
1
Kudos
Add Kudos
Bookmarks
Bookmark this Post
General Discussion
User avatar
PrashantPonde
Joined: 27 Jun 2012
Last visit: 29 Jan 2025
Posts: 311
Own Kudos:
2,781
 [8]
Given Kudos: 185
Concentration: Strategy, Finance
Posts: 311
Kudos: 2,781
 [8]
5
Kudos
Add Kudos
2
Bookmarks
Bookmark this Post
User avatar
SVaidyaraman
Joined: 17 Dec 2012
Last visit: 11 Jul 2025
Posts: 566
Own Kudos:
1,833
 [1]
Given Kudos: 20
Location: India
Expert
Expert reply
Posts: 566
Kudos: 1,833
 [1]
1
Kudos
Add Kudos
Bookmarks
Bookmark this Post
HiteshPunjabi
Which of the following is equal to (0.9998) 2 ?



0.99950014


0.99950234


0.99960004


0.99960064


0.99961024


Dear Hitesh,

You see the difference between the numbers starts from the last but one digit. So it is enough to multiply and get the last two digits only. Here in the case of 0.9998 x 0.9998, multiply only 98 and 98, you get 9604. The last but one digit is 0 which is only in choice C.
avatar
BizSchoolorBust
Joined: 06 Apr 2013
Last visit: 28 Nov 2016
Posts: 24
Own Kudos:
Given Kudos: 20
Location: United States
Concentration: Technology, Entrepreneurship
GMAT 1: 640 Q42 V36
GPA: 3.56
WE:Consulting (Consulting)
GMAT 1: 640 Q42 V36
Posts: 24
Kudos: 23
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Archit143
What is the value of the following (0.9998)^2 ?

A 0.99950014
B 0.99950234
C 0.99960004
D 0.99960064
E 0.99961024

I began to multiply .9998 x .9998. I knew the units digit would be 4 (8 x 8 = 64) and then I figured out the hundreds digit by multiplying 9 x 8 + 6 (from the 64) = 84. Rather than doing the rest of the math, I skipped to the tens digit in the second figure. That gave me 9 x 8 = 72 or 2 in the tens column plus the 8 gave me 04 for the first two digits. Figured out it was C.
User avatar
Zarrolou
Joined: 02 Sep 2012
Last visit: 11 Dec 2013
Posts: 842
Own Kudos:
Given Kudos: 219
Status:Far, far away!
Location: Italy
Concentration: Finance, Entrepreneurship
GPA: 3.8
Posts: 842
Kudos: 5,185
Kudos
Add Kudos
Bookmarks
Bookmark this Post
\((0.9998)^2=(1-0.0002)^2=(1-2*10^-^4)^2=1+2^2*10^-^8-2*2*10^-^4\) it's the old formula \((a+b)^2=a^2+b^2+2ab\)

\(1+4*10^-^8-4*10^-^4=1+0.00000004-0.0004\)

\((1-0.0004)+0.00000004\)
\(0.9996+0.00000004=0.99960004\)
C
User avatar
Archit143
Joined: 21 Sep 2012
Last visit: 20 Sep 2016
Posts: 721
Own Kudos:
Given Kudos: 70
Status:Final Lap Up!!!
Affiliations: NYK Line
Location: India
GMAT 1: 410 Q35 V11
GMAT 2: 530 Q44 V20
GMAT 3: 630 Q45 V31
GPA: 3.84
WE:Engineering (Transportation)
Kudos
Add Kudos
Bookmarks
Bookmark this Post
thnks Zarrolu
i followed the same method....bt i missed ...thnks maan

Archit
User avatar
Transcendentalist
Joined: 24 Nov 2012
Last visit: 04 Dec 2023
Posts: 127
Own Kudos:
Given Kudos: 73
Concentration: Sustainability, Entrepreneurship
GMAT 1: 770 Q50 V44
WE:Business Development (Internet and New Media)
GMAT 1: 770 Q50 V44
Posts: 127
Kudos: 1,068
Kudos
Add Kudos
Bookmarks
Bookmark this Post
It just faster to do criss cross multiplication in this question and you can get the answer in less than 30 secs.

9 9 9 8

9 9 9 8

Units place : 8 x 8 = 64 => Units place is 4 with carry over of 4

Tens place : 9x8 + 9x8 + 6 = 150 => Tens place is 0 with carry over of 15

You can stop here since you have already found answer by checking options

This is criss cross multiplication technique from vedic mathematics (https://www.brighthubeducation.com/homew ... thematics/) and i would highly recommend looking it up.

Elaborating 100's place : 9x8 + 9x9 + 9x8 +15 = 240 => 100s place is 0 with carry over 24

1000 place : 9x8 +9x9 + 9x9 + 9x8 + 24 = 330 => 1000 place is 0 with carry over 33 and so on....
User avatar
mau5
User avatar
Verbal Forum Moderator
Joined: 10 Oct 2012
Last visit: 31 Dec 2024
Posts: 478
Own Kudos:
3,386
 [1]
Given Kudos: 141
Posts: 478
Kudos: 3,386
 [1]
1
Kudos
Add Kudos
Bookmarks
Bookmark this Post
HiteshPunjabi
Which of the following is equal to 0.9998^2 ?

A. 0.99950014
B. 0.99950234
C. 0.99960004
D. 0.99960064
E. 0.99961024

For the sake of convenience, let us assume it to be= 9998*9998 = 9998*(10000-2) = 99980000-19996 --> the units digit is 4 and the tens a 0. Only C satisfies.

C.
User avatar
Temurkhon
Joined: 23 Jan 2013
Last visit: 06 Apr 2019
Posts: 408
Own Kudos:
Given Kudos: 43
Schools: Cambridge'16
Schools: Cambridge'16
Posts: 408
Kudos: 325
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Multiplying

0.9998
0.9998
______
------84
----82
______
------04 in the end


only C
avatar
PareshGmat
Joined: 27 Dec 2012
Last visit: 10 Jul 2016
Posts: 1,531
Own Kudos:
Given Kudos: 193
Status:The Best Or Nothing
Location: India
Concentration: General Management, Technology
WE:Information Technology (Computer Software)
Posts: 1,531
Kudos: 8,270
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Just for sake of convenience, remove decimal from the question as well from the answer

\(9998^2 = (10^4 - 2)^2 = 100000000 + 4 - 40000 = 100000004 - 40000\)

Last 2 digits are 04

Answer = C
User avatar
Sabby
Joined: 17 Jun 2018
Last visit: 04 Mar 2026
Posts: 84
Own Kudos:
Given Kudos: 397
Location: France
GPA: 3.85
Posts: 84
Kudos: 118
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Hi,

You just need to consider the 2 last digits to find the right answer.
98^2=9604 =>look at the 2 last digits it's 04, therefore only Answer C) satisfies.
User avatar
Keshav1404
Joined: 11 Jun 2022
Last visit: 21 Apr 2026
Posts: 65
Own Kudos:
Given Kudos: 48
GMAT 1: 660 Q48 V32
GMAT 1: 660 Q48 V32
Posts: 65
Kudos: 19
Kudos
Add Kudos
Bookmarks
Bookmark this Post
HiteshPunjabi
Which of the following is equal to 0.9998^2 ?

A. 0.99950014
B. 0.99950234
C. 0.99960004
D. 0.99960064
E. 0.99961024

M15-07


We can use the identity:

(a - b)^2 = a^2 - 2ab + b^2

In this case, we can let a = 1 and b = 0.0002 (since 0.9998 is 1 - 0.0002):

(1 - 0.0002)^2 = 1^2 - 2(1)(0.0002) + 0.0002^2
= 1 - 0.0004 + 0.00000004
= 0.99960004

Therefore, 0.9998^2 is equal to 0.99960004. Option C is correct.
User avatar
bumpbot
User avatar
Non-Human User
Joined: 09 Sep 2013
Last visit: 04 Jan 2021
Posts: 38,956
Own Kudos:
Posts: 38,956
Kudos: 1,117
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Automated notice from GMAT Club BumpBot:

A member just gave Kudos to this thread, showing it’s still useful. I’ve bumped it to the top so more people can benefit. Feel free to add your own questions or solutions.

This post was generated automatically.
Moderators:
Math Expert
109740 posts
Tuck School Moderator
853 posts