A desert outpost has a water supply that is sufficient to last 21 days

Question

A desert outpost has a water supply that is sufficient to last 21 days for 15 people. At the same average rate of water consumption per person, how many days would the water supply last for 9 people?

A. 28.0
B. 32.5
C. 35.0
D. 37.5
E. 42.0

EgmatQuantExpert · Answer

Solution

Given:  
 • The existent water supply is sufficient to last 21 days for 15 people
• The average consumption rate for each person is same

To find:  
 • The same water supply would last for how many days, if there are 9 people

Approach and Working:  
If we assume that the consumption for every person per day is x, then
 • Total amount of water supply = 21 * 15 * x

For 9 people, if this supply is sufficient for d days, then we can write
 • 9 * d * x = 21 * 15 * x
Or, d =  21 * \frac{15}{9}  = 35

Hence, the correct answer is option C.

Answer: C

Lowkya · Answer

Assume 1 person / 1 day. water consumed = x.
15 persons/ 1 day = 15x.
15 persons for 21 days = 15x * 21.
Then 9 persons / 1 day = 9x.
Number of days 9 persons will take =  \frac{(15x * 21)}{9x} .
= 35.

Correct choice: C

KSBGC · Answer

15 people can use water for 21 days
1 people can use water for 21*15 days
9 people can use the water for  \frac{21*15}{9} 
 = 35 days

Thus the best answer is C.

SonalSinha803 · Answer

21 days for 15 people,
Thus, 21*15 days for one person.

For 9 people, it would last (21*15)/9 = 35 days.

Hence, option C is the right answer.

Posted from my mobile device

Archit3110 · Answer

total available water ; 21*15 
avg for 9 people ; 21*15/9 = 35
IMO C

AyushCrackVerbal · Answer

Let the water consumption per person per day be " x "

Water consumption by 15 people in 1 day = 15 x

Water consumption by 15 people in 21 days = 15 x  * 21 = 315 x

So the water available at desert outpost = 315 x

Now, water consumption by 9 people in 1 day = 9 x

Number of days water supply would last =  \frac{315x}{9x}  = 35 Days

The correct answer is  C

ScottTargetTestPrep · Answer

If we assume that a person consumes 1 gallon of water per day, then there must be 21 x 15 = 315 gallons of water for the 15 people to last 21 days. If there are 9 people, the 315 gallons of water will last 315/9 = 35 days.

Answer: C

BrentGMATPrepNow · Answer

Let's assign a "nice value"  to the amount of water that's available. 
Let's first day that each person drinks  1  liter of water EACH DAY. 
At that rate, the 15 people would drink a total of 15 liters EACH DAY.
So, in 21 days, they'd drink a total of  315  liters   315 ] .

Now let's see how long that  315  liters of water will last if there are only 9 people. 
If each person drinks  1  liter of water EACH DAY, then the 9 people would drink a total of 9 liters EACH DAY. 
So, the number of days it takes to drink all  315  =  315 /9 = 35

Answer: C

Cheers,
Brent

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A desert outpost has a water supply that is sufficient to last 21 days

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