Question

How many even numbers are there with three digits so that if 5 is one of the digits then 7 is the next digit?

Answer 1

So numbers are570,572,574,576,578=5 numbers. Other 3digits numbers can be formed as (1) unit digit can be taken from0,2,4,6,8 i.e 5 ways. (3)Hundredth digit can be taken from 1 to 9 except 5.Thus8 possible cases. Hence 8*9*5+5=365such numbers can be made.