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25 Jun 2018, 05:02
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Over the past 7 weeks, the Smith family had weekly grocery bills of $74,$69, $64,$79, $64,$84, and $77. What was the Smiths' average (arithmetic mean) weekly grocery bill over the 7-week period? A.$64

B. $70 C.$73

D. $74 E.$85

NEW question from GMAT® Official Guide 2019

(PS07369)

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##### Most Helpful Expert Reply
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Joined: 22 May 2016
Posts: 3725
Over the past 7 weeks, the Smith family had weekly grocery bills of $7 [#permalink] ### Show Tags 27 Jun 2018, 18:28 7 9 Bunuel wrote: Over the past 7 weeks, the Smith family had weekly grocery bills of$74, $69,$64 $79,$64, $84, and$77. What was the Smiths' average (arithmetic mean) weekly grocery bill over the 7-week period?

A. $64 B.$70

C. $73 D.$74

### Show Tags

29 Jun 2018, 06:58
28
9
First, choose a nice, round number, such as 70, within the range of values.

Then calculate the average with the following formula:

Average = Nice number + Average of differences from the nice number

Average = 70 + (4 - 1 - 6 + 9 - 6 + 14 + 7)/7 = 70 + 21/7 =73

Answer: C
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Re: Over the past 7 weeks, the Smith family had weekly grocery bills of $7 [#permalink] ### Show Tags 25 Jun 2018, 05:10 Solution Given: • Over the past 7 weeks, the Smith family had weekly grocery bills of$74, $69,$64, $79,$64, $84, and$77

To find:
• Smith’s average weekly grocery bill over the 7-week period

Approach and Working:
• Smith’s total bill amount over the 7-week period = (74 + 69 + 64 + 79 + 64 + 84 + 77) = 511
• Therefore, Smith’s average bill amount over the same period = $$\frac{511}{7}$$ = 73

Hence, the correct answer is option C.

Answer: C
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28 Jun 2018, 18:07
1
Bunuel wrote:
Over the past 7 weeks, the Smith family had weekly grocery bills of $74,$69, $64,$79, $64,$84, and $77. What was the Smiths' average (arithmetic mean) weekly grocery bill over the 7-week period? A.$64

B. $70 C.$73

D. $74 E.$85

We can determine the average using the formula: average = sum / number:

average = (74 + 69 + 64 + 79 + 64 + 84 + 77)/7 = 511/7 = 73

Answer: C
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Re: Over the past 7 weeks, the Smith family had weekly grocery bills of $7 [#permalink] ### Show Tags 28 Aug 2018, 03:42 Bunuel wrote: Over the past 7 weeks, the Smith family had weekly grocery bills of$74, $69,$64, $79,$64, $84, and$77. What was the Smiths' average (arithmetic mean) weekly grocery bill over the 7-week period?

A. $64 B.$70

C. $73 D.$74

E. $85 NEW question from GMAT® Official Guide 2019 (PS07369) Easy way out is consider avg 70 - so diff for all terms is 4, -1 , -6, 9 , -6,14, 7 = sum is 21 = divided by 7 = equal to 3 so 70 +3 = 73 avg Board of Directors Status: QA & VA Forum Moderator Joined: 11 Jun 2011 Posts: 4868 Location: India GPA: 3.5 WE: Business Development (Commercial Banking) Re: Over the past 7 weeks, the Smith family had weekly grocery bills of$7  [#permalink]

### Show Tags

10 Sep 2018, 07:34
Bunuel wrote:
Over the past 7 weeks, the Smith family had weekly grocery bills of $74,$69, $64,$79, $64,$84, and $77. What was the Smiths' average (arithmetic mean) weekly grocery bill over the 7-week period? A.$64

B. $70 C.$73

D. $74 E.$85

NEW question from GMAT® Official Guide 2019

(PS07369)

$$\frac{( 70 + 4 ) + ( 70 - 1 ) + ( 60 + 4 ) + ( 80 - 1 ) + ( 60 + 4 ) + ( 80 + 4 ) + ( 70 + 7 )}{7}$$

= $$\frac{( 70 + 70 + 60 + 80 + 60 + 80 + 70 ) + ( 4 - 1 + 4 - 1 + 4 + 4 + 7 )}{7}$$

= $$\frac{490 + 21}{7}$$

= $$\frac{490}{7} + \frac{21}{7}$$

= $$70 + 3$$

= $$73$$, Answer must be (C)
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02 Oct 2018, 00:09
1
This solution might be too blunt for some people. Sum the unit digits and you will have 41.
Now there are 7 numbers, which mean if x multiply by 7 must will result a number with unit digit of 1, so the x is 3.
The only answer with 3 as its unit digit is C.
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27 Jan 2020, 12:45
Notice that all options' values have different unit digit;

To Solve: Add the unit digits of each values(4+9+4+9+4+4+7) = 41 and check the unit digit of output (unit digit 1).

for division by 7, 3 should be unit digit of the quotient.

Only Option C satisfies, it is $73! _________________ Unable to Give Up! Re: Over the past 7 weeks, the Smith family had weekly grocery bills of$7   [#permalink] 27 Jan 2020, 12:45
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