A total of (7 + 3) persons = 10 personal can sit in 10! ways.If we consider three girls as one unit, total persons = 7 + = 8 (here all three girls sit together).No. of ways = 81 and the three girls can be arranged in 31 ways among themselves.So, the total number of ways when three girls sit together = 81 x 31When the girls don't sit together, number of ways = 101 - (81 x 31) = 81 (10 x 9 - 6) = 81 x 84 = 3386880
Let the middle digit be x. Then, 2x = 10 or x = 5.So, the number is either 253 or 352. Since the number increases on reversing the digits, so the hundred's digit is smaller than the unit's digit. Hence, required number = 253.
EXAMIANS