At 15:00, 20 students were in the computer lab. Starting at 15:03, and

Question

At 15:00, 20 students were in the computer lab. Starting at 15:03, and every three minutes thereafter, 3 students entered the lab. Meanwhile, beginning at 15:10 and every ten minutes thereafter, 8 students exited the lab. How many students were in the computer lab at 15:44?

A. 7
B. 14
C. 25
D. 27
E. 30

A. 7
B. 14
C. 25
D. 27
E. 30

CareerGeek · Accepted Answer

From 15:03 till 15:44, number of multiples of 3 are 14 = 3*14 = 42 students entered the lab
So, Total students entered lab = 42

From 15:10 till 15:44, number of 10 multiples are 4 = 4*8 = 32 students left the lab

So, Net students present in lab at 15:44 = 20 + 42 - 32 = 30

IMO Option E

Lampard42 · Answer

Number of multiples of 3 in 44 minutes = 44/3=14 so 42 additions
Number of multiples of 10 in 44 min = 4 so 32 deletions
So Net 10 addition to 20 IMO E 30

Archit3110 · Answer

from 1500 to 1544 total students entered ; 14*3 ; 42 and left ; 32
net ; 42-32 ; 10 
inital class was of 20 @ 1500 so total students; 10+20 ; 30 @ 15:44 
IMO E

Bunuel · Answer

Students began entering the lab every 3 minutes starting at 15:03 and continued until 15:42. This gives a total of  \frac{42-3}{3} + 1 = 14  intervals where 3 students each entered. On the other hand, students started leaving the lab every 10 minutes beginning at 15:10 and the last group left at 15:40, resulting in  \frac{40-10}{10} + 1 = 4  intervals where groups of 8 students each departed. Therefore, the net increase in students in the lab is  14*3 - 4*8 = 6 .

Answer: E

onlymalapink · Answer

the only problem in this question was coming to terms with the fact that the 3 minutes progression never stopped tho the question never really elucidates either way.

At 15:00, 20 students were in the computer lab. Starting at 15:03, and

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