The sum of the digits of a number formed by any power or index of 9 is always 9.
(v) 9 x 7 = 63 → 6 + 3 = 9
(vi) 9 x 15 = 135 → 1 + 3 + 5 = 9
(vii) 9 x 17 = 153 → 1 + 5 + 3 = 9
(viii) 9 x 19 = 171 → 1 + 7 + 1 = 9
`Related Concept
● Patterns and Mental Mathematics
● Counting Numbers in Proper Pattern
● Puzzle
● Patterns
4th Grade Math Activities
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