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17 Aug 2018, 12:26
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15% (low)

Question Stats:

81% (01:31) correct 19% (01:26) wrong based on 94 sessions

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Chu-Li has $100 in her piggy bank. How much will she have in her bank 40 weeks from now if she puts$1 in the bank next week, $2 two weeks from now,$3 three weeks from now, and continues to increase the amount that she puts in by $1 each week? A.$140
B. $800 C.$920
D. $1640 E.$1740

_________________
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Joined: 20 Feb 2015
Posts: 790
Concentration: Strategy, General Management
Re: Chu-Li has $100 in her piggy bank. How much will she have in her bank [#permalink] ### Show Tags 17 Aug 2018, 12:41 Bunuel wrote: Chu-Li has$100 in her piggy bank. How much will she have in her bank 40 weeks from now if she puts $1 in the bank next week,$2 two weeks from now, $3 three weeks from now, and continues to increase the amount that she puts in by$1 each week?

A. $140 B.$800
C. $920 D.$1640
E. $1740 100 + sum of 1st 40 terms 100 + 40(41)/2 100 + 820 920 C VP Status: Learning stage Joined: 01 Oct 2017 Posts: 1028 WE: Supply Chain Management (Energy and Utilities) Re: Chu-Li has$100 in her piggy bank. How much will she have in her bank  [#permalink]

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17 Aug 2018, 12:42
Bunuel wrote:
Chu-Li has $100 in her piggy bank. How much will she have in her bank 40 weeks from now if she puts$1 in the bank next week, $2 two weeks from now,$3 three weeks from now, and continues to increase the amount that she puts in by $1 each week? A.$140
B. $800 C.$920
D. $1640 E.$1740

Cumulative amount of money in 40 weeks: 1+2+3+...............+40=$$\frac{40*41}{2}$$=820

Total savings=Base deposit+Additional deposit in 40 weeks=100+820=$920 Ans. (C) _________________ Regards, PKN Rise above the storm, you will find the sunshine Intern Joined: 03 Sep 2017 Posts: 10 Location: India GMAT 1: 720 Q47 V42 GPA: 3.4 Re: Chu-Li has$100 in her piggy bank. How much will she have in her bank  [#permalink]

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17 Aug 2018, 16:08
PKN wrote:
Bunuel wrote:
Chu-Li has $100 in her piggy bank. How much will she have in her bank 40 weeks from now if she puts$1 in the bank next week, $2 two weeks from now,$3 three weeks from now, and continues to increase the amount that she puts in by $1 each week? A.$140
B. $800 C.$920
D. $1640 E.$1740

Cumulative amount of money in 40 weeks: 1+2+3+...............+40=$$\frac{40*41}{2}$$=820

Total savings=Base deposit+Additional deposit in 40 weeks=100+820=$920 Ans. (C) Hi, what formula is this through which we get 40*41/2? Posted from my mobile device VP Status: Learning stage Joined: 01 Oct 2017 Posts: 1028 WE: Supply Chain Management (Energy and Utilities) Chu-Li has$100 in her piggy bank. How much will she have in her bank  [#permalink]

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17 Aug 2018, 21:08
1
vedanths wrote:
PKN wrote:
Bunuel wrote:
Chu-Li has $100 in her piggy bank. How much will she have in her bank 40 weeks from now if she puts$1 in the bank next week, $2 two weeks from now,$3 three weeks from now, and continues to increase the amount that she puts in by $1 each week? A.$140
B. $800 C.$920
D. $1640 E.$1740

Cumulative amount of money in 40 weeks: 1+2+3+...............+40=$$\frac{40*41}{2}$$=820

Total savings=Base deposit+Additional deposit in 40 weeks=100+820=$920 Ans. (C) Hi, what formula is this through which we get 40*41/2? Posted from my mobile device Hi vedanths, The sum of first 'n' natural numbers:$$\frac{n(n+1)}{2}$$ Here we have to determine the sum of first 40 natural numbers,(1+2+...+40) Now put n=40 in the above sum formula.We have ,sum=40*(40+1)/2. Hope it helps. _________________ Regards, PKN Rise above the storm, you will find the sunshine Intern Joined: 03 Sep 2017 Posts: 10 Location: India GMAT 1: 720 Q47 V42 GPA: 3.4 Re: Chu-Li has$100 in her piggy bank. How much will she have in her bank  [#permalink]

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18 Aug 2018, 02:45
PKN wrote:
Hi vedanths,

The sum of first 'n' natural numbers:$$\frac{n(n+1)}{2}$$

Here we have to determine the sum of first 40 natural numbers,(1+2+...+40)
Now put n=40 in the above sum formula.We have ,sum=40*(40+1)/2.

Hope it helps.

Yes got it, thank you!
Target Test Prep Representative
Affiliations: Target Test Prep
Joined: 04 Mar 2011
Posts: 2822
Re: Chu-Li has $100 in her piggy bank. How much will she have in her bank [#permalink] ### Show Tags 20 Aug 2018, 11:05 1 Bunuel wrote: Chu-Li has$100 in her piggy bank. How much will she have in her bank 40 weeks from now if she puts $1 in the bank next week,$2 two weeks from now, $3 three weeks from now, and continues to increase the amount that she puts in by$1 each week?

A. $140 B.$800
C. $920 D.$1640
E. $1740 Since sum = average x quantity and we have a set of evenly spaced numbers: The average of an evenly spaced set of numbers is (smallest + greatest)/2, so average = (1 + 40)/2 = 41/2 sum = 41/2 x 40 = 41 x 20 = 820 Since she started with 100 dollars, she will have 920 dollars after 40 weeks. Answer: C _________________ # Jeffrey Miller Head of GMAT Instruction Jeff@TargetTestPrep.com 122 Reviews 5-star rated online GMAT quant self study course See why Target Test Prep is the top rated GMAT quant course on GMAT Club. Read Our Reviews If you find one of my posts helpful, please take a moment to click on the "Kudos" button. Re: Chu-Li has$100 in her piggy bank. How much will she have in her bank   [#permalink] 20 Aug 2018, 11:05
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