On a Monday in a certain restaurant, 20 percent of the

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Gmat_mission: Legendary Member; Posts: 1622; Joined: Thu Mar 01, 2018 7:22 amFollowed by: 2 members

by Gmat_mission » Sat Apr 14, 2018 3:18 am

On a Monday in a certain restaurant, 20 percent of the 180 customers ordered the daily special. On Tuesday, only 10 percent of the 120 customers ordered the special. For the two days combined, what percent of the customers ordered the daily special?

A. 15%
B. 16%
C. 18%
D. 23%
E. 30%

[spoiler]OA=B[/spoiler].

How should I solve this PS question? What are the formulas that I should use? Thanks.

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Source: Beat The GMAT — Problem Solving | Sat Apr 14, 2018 3:18 am

Vincen: Legendary Member; Posts: 2898; Joined: Thu Sep 07, 2017 2:49 pmFollowed by: 5 members; Thanked: 6 times

by Vincen » Sat Apr 14, 2018 6:01 am

Gmat_mission wrote:On a Monday in a certain restaurant, 20 percent of the 180 customers ordered the daily special. On Tuesday, only 10 percent of the 120 customers ordered the special. For the two days combined, what percent of the customers ordered the daily special?

A. 15%
B. 16%
C. 18%
D. 23%
E. 30%

[spoiler]OA=B[/spoiler].

How should I solve this PS question? What are the formulas that I should use? Thanks.

Hello Gmat_mission.

On a Monday in a certain restaurant, 20 percent of the 180 customers ordered the daily special, that is to say, 20%*180 = 36 customers.

On Tuesday, only 10 percent of the 120 customers ordered the special, that is to say, 10%*120 = 12 customers.

The total number of customers (Monday and Tuesday) is: 180 + 120 = 300.
The total number of customers that ordered the daily special (Monday and Tuesday) is: 36 + 12 = 48.

Now, if 300 customers is the 100%, then 48 customers represents the $$x=\frac{48\cdot100}{300}\%=\frac{4800}{300}\%=16\%.$$ Hence, the correct answer is B.

I hope it helps.

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Brent@GMATPrepNow: GMAT Instructor; Posts: 16207; Joined: Mon Dec 08, 2008 6:26 pmFollowed by: 1268 members; Location: Vancouver, BC; Thanked: 5254 times; GMAT Score:770

by Brent@GMATPrepNow » Sat Apr 14, 2018 6:52 am

Gmat_mission wrote:On a Monday in a certain restaurant, 20 percent of the 180 customers ordered the daily special. On Tuesday, only 10 percent of the 120 customers ordered the special. For the two days combined, what percent of the customers ordered the daily special?

A. 15%
B. 16%
C. 18%
D. 23%
E. 30%

On a Monday in a certain restaurant, 20 percent of the 180 customers ordered the daily special.
10% of 180 = 18
So, 20% of 180 = 36
So, 36 people ordered the daily special on MONDAY

On Tuesday, only 10 percent of the 120 customers ordered the special.
10% of 120 = 12
So, 12 people ordered the daily special on TUESDAY

For the two days combined, what percent of the customers ordered the daily special?
TOTAL number of people who ordered the daily special = 36 + 12 = 48 people
TOTAL number of customers for the two days = 180 + 120 = 300

So 48/300 of the customers ordered the special.
Our job is to rewrite 48/300 as a PERCENT. Here's one approach:
Take: 48/300
Divide top and bottom by 3 to get the EQUIVALENT fraction 16/100
16/100 = 16%

Answer: B

Cheers,
Brent

Brent Hanneson - Creator of GMATPrepNow.com

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swerve: Legendary Member; Posts: 2535; Joined: Sun Oct 29, 2017 2:04 pmFollowed by: 6 members

by swerve » Sat Apr 14, 2018 9:59 am

Just solving for the numbers should take you to the answer easily here.

Monday: 20% of 180 ordered daily special.
Therefore 36 ordered daily special.

Tuesday: 10% of 120 ordered daily special.
Therefore 12 ordered daily special.

Total daily special = 48
Total people on Monday and Tuesday = 180 + 120 = 300.

Percentage of people who ordered daily special = (48/300)*100 = 16%. Option B.

Regards!

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Scott@TargetTestPrep: GMAT Instructor; Posts: 8137; Joined: Sat Apr 25, 2015 10:56 amFollowed by: 29 members; Location: Los Angeles, CA; Thanked: 43 times

by Scott@TargetTestPrep » Wed Apr 25, 2018 3:48 pm

Gmat_mission wrote:On a Monday in a certain restaurant, 20 percent of the 180 customers ordered the daily special. On Tuesday, only 10 percent of the 120 customers ordered the special. For the two days combined, what percent of the customers ordered the daily special?

A. 15%
B. 16%
C. 18%
D. 23%
E. 30%

On the first day 0.2 x 180 = 36 customers ordered the special.

On the second day 0.1 x 120 = 12 ordered the special.

We combine the data for the two days. Thus, (36 + 12)/(180 + 120) = 48/300 = 0.16 = 16% of the customers ordered the special.

Answer: B

Scott Woodbury-Stewart
Founder and CEO
[email protected]

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