Multiplying By 25:
A. Multiplying by 25 is one of the basic multiplication methods in number sense.
1. You can rewrite 25 to be 100/4. So the first step is to divide by 4 and write
this number down.
2. Depending on the remainder,referred to as (n MOD 4), the last numbers are
the following:
a) If (n MOD 4) = 0 then the last numbers are 00.
b) If (n MOD 4) = I then the last numbers are 25.
c) If (n MOD 4) = 2 then the last numbers are 50.
d) If (n MOD 4) = 3 then the last numbers are 75.
B. Examples:
Ex [1] 25 x 84 = -----------
a) 84/4 = 21. Write 21.
b) Since there is no remainder the last numbers are 00.
c) Tne answer is 2100.
Ex [2] 113 x 25 = ----------
a) 113/4 = 18 with a remainder of 1. Write 18.
b) The last numbers are 25.
c)The answer is 1825.
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