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

Redeem

digits 71*72*

This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
User avatar
Master | Next Rank: 500 Posts
Posts: 435
Joined: Mon Mar 15, 2010 6:15 am
Thanked: 32 times
Followed by:1 members

digits 71*72*

by eaakbari » Thu Apr 15, 2010 3:38 am
what are the last two digits of the expression 71*72*73*... and so on till 79?


a50
b 70
c 00
d 80


Source GRE prep material
Sorry but dont have OA or OE
Whether you think you can or can't, you're right.
- Henry Ford
Top
Source: — Problem Solving |
Legendary Member
Posts: 576
Joined: Sat Mar 13, 2010 8:31 pm
Thanked: 97 times
Followed by:1 members

by liferocks » Thu Apr 15, 2010 7:01 am
the ans will be divisible by 100 as the numbers has 75=25x3 as well as 4 in it.
hence last 2 digits will be [spoiler]C) 00[/spoiler]
Top
Junior | Next Rank: 30 Posts
Posts: 11
Joined: Thu Apr 15, 2010 6:48 am
Thanked: 1 times

by hachette » Thu Apr 15, 2010 7:08 am
75 x 4 = 300
the last two digits are 00
Top
User avatar
Master | Next Rank: 500 Posts
Posts: 435
Joined: Mon Mar 15, 2010 6:15 am
Thanked: 32 times
Followed by:1 members

by eaakbari » Thu Apr 15, 2010 8:38 am
Oh yes, I am silly, took 75 as a single 5. Thanks guys
Whether you think you can or can't, you're right.
- Henry Ford
Top
Senior | Next Rank: 100 Posts
Posts: 52
Joined: Sat Jan 23, 2010 9:08 pm
Thanked: 2 times

by Ashish8 » Thu Apr 15, 2010 10:14 am
This is how I did it as I didn't understand hachette or liferocks.

Someone can correct me if its the wrong approach

We know 74 * 75 will yield one 0 at the end. The last two digits will be 50.

50 * 76 will yield two 0's at the end. After that everything will yield 2 0's at the end.
Top
Post new topic Post Reply
• Page 1 of 1