Math Tricks for Number Theory Finda Dwi Permatahati (110210101011) Dini Mustika Sari (110210101013) Fajri Maulana (110210101014)
Math tricks for number theory (revision)
Nov 28, 2014
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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