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It's about the multiplication of 25 and the uniqueness of 9.
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Math Tricks for Number Theory
Finda Dwi Permatahati (110210101011)
Dini Mustika Sari (110210101013)
Fajri Maulana (110210101014)
Multiplication by 25
24 x 25 =
?
: 4 = 6
= 600= 6 x 100
1
2
Comparing two methods24 x 25 =: 4 = 6
24 x 25 =
2425
x 120
+600 = 60048
?= 6 x 100
1
2
Multiplication by 25
123 x 25 =
?
: 4 = 30, remain=3
= (30 x 100) + (3 x 25)= 3000 + 75= 3075
1
2
Exercises
4545 x 25 = ?278 x 25 =
?
12
The Uniqueness of Number
918 is multiple of 927 is multiple of 936 is multiple of 9
1 + 8 = 92 + 7 = 93 + 6 = 9
The Uniqueness of Number
2468a7
2+4+6+8+a+7= 9k
Integer number a+27=
9k a = 0 or a = 9
9
Proof
246807 : 9 = 27423246897 : 9 = 27433
There’s no remain
Exercise
4545450009321
24376p
12
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