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12 Jan 2024, 02:30
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C
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
35%
(medium)
Question Stats:
74% (01:54) correct
26%
(02:30)
wrong
based on 121
sessions
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In a theater, the first row has 16 seats and each row after has 2 more seats than the one before. If the last row has 64 seats, how many seats are there altogether?
A. 640
B. 720
C. 1,000
D. 1,200
E. 1,240
A. 640
B. 720
C. 1,000
D. 1,200
E. 1,240
In a certain theater, the first row has 16 seats and the next row has 2 more seats than previous row. If the last row has 64 seats, what is the total number of seats?
Aryaa03
Joined: 12 Jun 2023
Last visit: 19 Feb 2026
Posts: 210
Given Kudos: 159
Location: India
Schools: ISB '27 (A) IIM Calcutta '26 (A) IIMA '26 (D)
GMAT Focus 1: 645 Q86 V81 DI78 
12 Jan 2024, 03:01
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Bunuel
Sol:
IMO-Option-C
Seats in:
1st row = 16
2nd row =16 + 2 = 18
3rd row = 16 + 2 + 2 = 20
.
.
nth row = 16 + (n-1)*2 = 64 , Therefore, n= 25
This is an A.P wih a = 16 and d=2
Sum of all seats = n/2*(2*a + (n-1)*d) = 25/2*(2*16 + (25-1)*2) = 25*80/2 = 1000
12 Jan 2024, 06:57
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Answer: C
16, 18, 64, 60
20, 22, 24, 26, 28
same for 30, 40 & 50
(2+4+6+8)*5 = 100
10*2 = 20
60*3 = 180
20*5 = 100
30*5 = 150
40*5 = 200
50*5 = 250
Total = 1,000
16, 18, 64, 60
20, 22, 24, 26, 28
same for 30, 40 & 50
(2+4+6+8)*5 = 100
10*2 = 20
60*3 = 180
20*5 = 100
30*5 = 150
40*5 = 200
50*5 = 250
Total = 1,000
