Find number of digits in `18^20`

If log2=0.30103, then the number of digit in 5^(20) is a.14 b.16 c.18 d.25

If log2=0.30103, the number of digit is 2^(64) is a.18b.19c.20d.21

Find the sum of digits of range of data : 13, 18, 20, 15, 12, 17, 9, 14, 11 and 16

If the number obtained by interchanging the digits of a two digit number is 18 more than the original number and the sum of the digits is 8 then what is the original number?

If the number obtained on the interchanging the digits of two-digit number is 18 more than the original number and the sum of the digits is 8, then what is the Reversed number?