How to add variables

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ISEE Middle Level Quantitative Reasoning › How to add variables

Questions 1 - 10
1

Add the following:

Explanation

In the problem

we will first insert a coefficient on the second term. When a variable stands alone, it has a coefficient of 1. So,

When adding variables, we can look at the variables as objects, then combine those objects.

Now, we can think of the variable a as cars. So, we can look at it as

We can think of it like this: If we see 5 cars pass by us on the road, and we see 1 more car pass us, how many cars have passed us? The answer is 6. There were 6 cars that passed us. So,

We add variables the same way.

2

Simplify:

Explanation

First, group together your like variables:

The only like variables needing to be combined are the x-variables. You can do this in steps or all at once:

3

Simplify the following:

Explanation

When solving this problem we need to remember our order of operations, or PEMDAS.

PEMDAS stands for parentheses, exponents, multiplication/division, and addition/subtraction. When you have a problem with several different operations, you need to solve the problem in this order and you work from left to right for multiplication/division and addition/subtraction.

Parentheses: We are not able to add a variable to a number, so we move to the next step.

Multiplication: We can distribute (or multiply) the .

Addition/Subtraction: Remember, we can't add a variable to a number, so the is left alone.

Now we have

4

Simplify the followng:

Explanation

When adding variables together, you must first make sure you are combining the same variable. So, in this case

we can see that both terms contain the variable a. Therefore, we can combine them.

Now, when we combine them, we can think of the variables as objects. So, we can say were are combining an apple and 4 apples together. So,

We can simplify our problem the same way.

5

Simplify the following expression:

Cannot be computed

Explanation

When adding and subtracting variable, you can only combine like variables.

That means all of the variables are solved separately from the variables.

Then you just add and subtract the constants normally so and .

So the final answer is .

6

Bob and Anita drove cross country together. If Bob drove miles on the trip, and Anita drove twice as many miles as Bob, how many miles total did they drive together?

Explanation

If Bob drove miles, and Anita drove twice as many miles as Bob, then Anita drove miles; therefore, the sum of the miles that they drove together would be 3J.

Thus, the correct answer is .

7

Combine the following:

Explanation

When combining variables, we can think of the variables as objects. So, in the problem

we can think of the variable m as movies. So, we can write it like this:

We can read it like this: We have 2 movies. We go to the store, and we buy 3 more movies. How many movies do we have now? We have 5 movies. So,

We add variables the same way.

8

is a positive integer.

Which is the greater quantity?

(A)

(B)

(A) and (B) are equal

It is impossible to determine which is greater from the information given

(A) is greater

(B) is greater

Explanation

Regardless of the value of , the expressions are equal.

9

Combine the following:

Explanation

To add variables, we will look at the variables like objects. So in the problem

we will think of a as being apples. So we can read this problem as

So, if we have 3 apples, and we go to the market and we buy 6 more apples, how many apples do we now have?

We add variables the same way. So,

We can look at this as we have 3 of something, we want to add 6 more somethings, so how many do we have now?

10

Solve for .

Explanation

First, combine all like terms, so we are left with

.

Then to isolate the variable (get it alone), we divide each side by 10 and are left with

.

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