A group of 630 children is arranged in rows for a group photograph session. Each row contains three fewer children than the row in front of it. What number of rows is not possible?
a. 3
b. 4
c. 5
d. 6
e. 7Let there be n rows and a students in the first row.
Number of students in the second row = a+ 3
Number of students in the third row = a+ 6 and so on.
The number of students in each row forms an arithmetic progression with common difference = 3.
The total number of students = The sum of all terms in the arithmetic progression.
=n[2a+3(n−1)]/2=630
Now consider options.
1. n=3, a=207
2. n=4,a=153
3. n=5,a=120
4. n=6,a=195/2
5. n=7,a=8
Hence the only option not possible is when n=6Write Here