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=6**Write Here**