act-dog

From the given data,

abc – cba + 396c = 990

100a + 10b + c – (100c + 10b + a) + 396c = 990

99a – 99c + 396c = 990

Observe that each term is divisible by 99. So on dividing the above expression by 99, we get

a – c + 4c = 10

a + 3c = 10

For c = 1, a = 7

c = 2, a = 4

c = 3, a = 1

'b' can take any value from 0 to 9

We have to find the value of M more than 300. So minimum value of 'a' should be 4.

So total possibilities are 402, 412, ...., 492 = 10 values

701, 711, ....., 791 = 10 values

So total values = 20.

Correct option: A