Help needed to solve calculus problem

If log 2 = 0.301, then what is the number of digits in 5^{20 ?}

Please tell me the procedure to solve these kind of problems

Start with the understanding that for any integer A, the number of digits is equal to log_10(A) rounded up to the next whole number. For example, the number of digits in the number 123456 is log_10(123456) = 5.09, which rounds up to 6. So for this problem the number of digits in 5^20 is log_10(5^20) rounded up. Since 5 = 10/2, you can use your log identities to determine log_10((10/2)^20). Can you take it from here?