All SAT Math Resources
Example Question #15 : Negative Numbers
Anytime a negative number is added, it is similar to subtraction. Recovert the expression to the correct form. Simplify.
The correct answer is .
Example Question #11 : Negative Numbers
Add the negative numbers:
In order to add the negative numbers, we need to eliminate the double signs and the parentheses. A positive and a negative sign will result in a negative sign.
Evaluate the terms on the right.
The answer is:
Example Question #14 : Integers
a, b, c are integers.
abc < 0
ab > 0
bc > 0
Which of the following must be true?
a – b > 0
a > 0
a + b < 0
ac < 0
b > 0
a + b < 0
Let's reductively consider what this data tells us.
Consider each group (a,b,c) as a group of signs.
From abc < 0, we know that the following are possible:
(–, +, +), (+, –, +), (+, +, –), (–, –, –)
From ab > 0, we know that we must eliminate (–, +, +) and (+, –, +)
From bc > 0, we know that we must eliminate (+, +, –)
Therefore, any of our answers must hold for (–, –, –)
This eliminates immediately a > 0, b > 0
Likewise, it eliminates a – b > 0 because we do not know the relative sizes of a and b. This could therefore be positive or negative.
Finally, ac is a product of negatives and is therefore positive. Hence ac < 0 does not hold.
We are left with a + b < 0, which is true, for two negatives added must be negative.