Question

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

Answer 1

If 3digit even numbers start with 5 then next digit is 7.So numbers are 570,572,574,576,578=5 numbers. Other 3digits numbers can be formed as (1) unit digit can be taken from 0,2,4,6,8 i.e 5 ways. (3)Hundredth digit can be taken from 1 to 9 except 5.Thus 8 possible cases. Hence 8*9*5+5=365 such numbers can be made.