1.What should be added to $15^{81}$ to make it divisible by 7 ? Suggest a general technique to counter problems like this.
2.For how many two-digit numbers, the sum of the digits is greater than the product of the digits?
1.What should be added to $15^{81}$ to make it divisible by 7 ? Suggest a general technique to counter problems like this.
2.For how many two-digit numbers, the sum of the digits is greater than the product of the digits?