what would be the no of digits in 4^{61}+4^{62}+4^{63}+4^{64}+4^{65}

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- Jan 4th 2013, 12:47 PMvjdmshortcut???????
what would be the no of digits in 4

^{61}+4^{62}+4^{63}+4^{64}+4^{65} - Jan 4th 2013, 01:29 PMHallsofIvyRe: shortcut???????
All of those numbers is less than or equal to so their sum is less than . so has 39 digits and 5 times that has 40 digits.

- Jan 4th 2013, 08:09 PMSorobanRe: shortcut???????
Hello, vjdm!

Quote:

We have: .

Take logs: .

m . . . . . . .

. . . . . . . . . . .

Therefore, has 40 digits.