Sat math Essentials

b
is 15 the divisor.
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N U M B E R S A N D O P E R AT I O N S R E V I E W
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4 7

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Odd and Even Numbers
An 
even
number is a number that can be divided by the number 2 to result in a whole number. Even numbers
have a 2, 4, 6, 8, or 0 in the ones place.
2
34
86
1,018
6,987,120
Consecutive even numbers
differ by two:
2, 4, 6, 8, 10, 12, 14 . . .
An 
odd
number cannot be divided evenly by the number 2 to result in a whole number. Odd numbers have
a 1, 3, 5, 7, or 9 in the ones place.
1
13
95
2,827
7,820,289
Consecutive odd numbers
differ by two:
1, 3, 5, 7, 9, 11, 13 . . .
Even and odd numbers behave consistently when added or multiplied:
even 
even 
even
and
even 
even 
even
odd 
odd 
even
and
odd 
odd 
odd
odd 
even 
odd
and
even 
odd 
even
Practice Question 
Which of the following situations must result in an odd number?
a.
even number 
even number
b.
odd number 
odd number
c.
odd number 
1
d.
odd number 
odd number
e.
even n
2
umber
Answer
b. a
,
c
, and 
d
definitely yield even numbers;
e
could yield either an even or an odd number. The product of
two odd numbers (
b
) is an odd number.
Dividing by Zero
Dividing by zero is impossible. Therefore, the denominator of a fraction can never be zero. Remember this fact
when working with fractions.
Example
n
5
4
We know that 
n
≠
4 because the denominator cannot be 0.