Question

4+44+444+....... sum up the following series​

Answer 1

$4 + 44 + 444 + ...... \\ 4(1 + 11 + 111+ .......) \\ \frac{4}{9} (9 + 99 + 999 + ....) \\ \frac{4}{9} ((10 - 1) + (100 - 1).....) \\ \frac{4}{9} \frac{10(10 {}^{n} - 1 - n) }{10 - 1} \\ \frac{4}{81} (10 {}^{ {}^{n + 1} } - 10 - n) \\ \frac{4(10 {}^{n + 1} - 10 - n) }{81}$

Answer 2

4932 maybe helpful answer