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

 It is currently 21 Nov 2018, 00:12

### 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 November
PrevNext
SuMoTuWeThFrSa
28293031123
45678910
11121314151617
18192021222324
2526272829301
Open Detailed Calendar
• ### All GMAT Club Tests are Free and open on November 22nd in celebration of Thanksgiving Day!

November 22, 2018

November 22, 2018

10:00 PM PST

11:00 PM PST

Mark your calendars - All GMAT Club Tests are free and open November 22nd to celebrate Thanksgiving Day! Access will be available from 0:01 AM to 11:59 PM, Pacific Time (USA)
• ### Free lesson on number properties

November 23, 2018

November 23, 2018

10:00 PM PST

11:00 PM PST

Practice the one most important Quant section - Integer properties, and rapidly improve your skills.

# M70-10

Author Message
TAGS:

### Hide Tags

Math Expert
Joined: 02 Sep 2009
Posts: 50712

### Show Tags

03 Sep 2018, 02:27
00:00

Difficulty:

(N/A)

Question Stats:

67% (01:10) correct 33% (02:56) wrong based on 3 sessions

### HideShow timer Statistics

A is the sum of the reciprocals of each of the integers from 3 to 7. B is the sum of the reciprocals of the even integers from 3 to 7. What is A – B?

A. $$\frac{10}{24}$$
B. $$\frac{61}{105}$$
C. $$\frac{71}{105}$$
D. $$\frac{2}{35}$$
E. $$\frac{7}{50}$$

_________________
Math Expert
Joined: 02 Sep 2009
Posts: 50712

### Show Tags

03 Sep 2018, 02:28
Official Solution:

A is the sum of the reciprocals of each of the integers from 3 to 7. B is the sum of the reciprocals of the even integers from 3 to 7. What is A – B?

A. $$\frac{10}{24}$$
B. $$\frac{61}{105}$$
C. $$\frac{71}{105}$$
D. $$\frac{2}{35}$$
E. $$\frac{7}{50}$$

We’ll go for PRECISE because all the information we need is in the question.

A is the sum of the reciprocals of each of the integers from 3 to 7, and B is the sum of the reciprocals of the even integers only. Written mathematically:

$$A = \frac{1}{3}+\frac{1}{4}+\frac{1}{5}+\frac{1}{6}+\frac{1}{7}$$, and $$B = \frac{1}{4}+\frac{1}{6}$$

Therefore, $$A - B= \frac{1}{3}+\frac{1}{4}+\frac{1}{5}+\frac{1}{6}+\frac{1}{7}- (\frac{1}{4}+\frac{1}{6})=\frac{1}{3}+\frac{1}{5}+\frac{1}{7}$$

We’ll find 3, 5 and 7’s lowest common denominator: 3 x 5 x 7 = 105.

Therefore, $$\frac{1}{3}+\frac{1}{5}+\frac{1}{7}=\frac{35+21+15}{105}=\frac{71}{105}$$.

_________________
Re M70-10 &nbs [#permalink] 03 Sep 2018, 02:28
Display posts from previous: Sort by

# M70-10

Moderators: chetan2u, Bunuel

 Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne Kindly note that the GMAT® test is a registered trademark of the Graduate Management Admission Council®, and this site has neither been reviewed nor endorsed by GMAC®.