2, .
5, 0 5.
. S :
S = n 10 n + n -1 10 n -1+... + 1 10 + 0.
, , , 2 5, 10 2 0 5.
S? 2 5? 0 ( ). a 0 2 Þ S 2, 0 5 Þ S 5( ). , S 2 Þ 0 2, S 5 Þ 0 5( ).
, S 2 Û 0 2; S 5 Û 0 5.
i , 0 ≤ i £ 9. 2 , 0, 2, 4, 6, 8, 5 , 0, 5. .
2 5 . 2 5 10 .
4 25.
4, , 4.
25, , 25, .. 00, 25, 50, 75.
. , 4 25 100. S , :
S = 10 n + n- 1 10 n -1 +... + 2 × 102 + 1 10 + 0.
, , 100, 4 25.
S 4 25 1 10 + 0,.. , . , S 4, 1 10+ 0 4. .
, S 25, 1 10 + 0 25, .. S 00, 25, 50, 75. .
, S 4 Û ( 1 10 + 0) 4; S 25 Û ( 1 10 + 0) 25.
3 9.
3, 3.
9, 9.
. S . :
S = an 10 n + an -1 10 n- 1 + + a1 10 + a0, an, an -1, , a 1, a 0 .
S :
, , , 9. .. , = n + n -1+... + 2 + 1 + 0, 9 ( ). 9, S 9.
, S 9 Þ m 9( ).
, S 9 Û (n + n -1+... + 2+ 1 + 0) 9.
3 , , , 3.
3 9 , 3 9 10 1, .. 1 . , 3 9 .
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