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A class photograph has to be taken. The first row consists of 6 girls who are sitting. 20 boys are standing behind the...
A class photograph has to be taken. The first row consists of 6 girls who are sitting. 20 boys are standing behind the girls. The two comer positions are reserved for the two tallest boys. In how many ways can the students be arranged ?
A
1440 × 6! ×2!
B
1440 × 720
C
1440 × 18! ×2!
D
1440 × 6!
E
1440 × 18!
A
1440 × 6! ×2!
B
1440 × 720
C
1440 × 18! ×2!
D
1440 × 6!
E
1440 × 18!
Solution
The number of ways in which girls can be arranged = 6! The number of ways in which two tall boys can be arranged = 2!The...
The number of ways in which girls can be arranged = 6!
The number of ways in which two tall boys can be arranged = 2!
The number of ways in which 18 boys can be arranged = 18!
The number of ways in which students can be arranged = (6!) × (2!) × (18!)
= 720 × 2 × 18!
= 1440 × 18!
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