Remember that "percent" means "per 100" and "of" means to multiply.

So 120% of 80% of 100 =

$\displaystyle 1.2 (.8)(100)=96$

and 130% of 70% of 105 =

$\displaystyle 1.3(.7)(105)=(.91)105=95.55$

Column A is greater.

$\displaystyle \frac{1}{2} \% \textrm{ of }1,000$ can be rewritten as $\displaystyle 0.5 \% \textrm{ of }1,000$, and restated as $\displaystyle 0.005 \times 1,000$. 

$\displaystyle 0.005 \times 1,000 = 5 > 0.5$

60% of 25,000 is equal to $\displaystyle 0.60 \times 25,000 = 15,000$

60% of that is $\displaystyle 0.60 \times 15,000 = 9,000$

50% of $\displaystyle N$ is equal to $\displaystyle 0.5N$.

20% of $\displaystyle 3N$ is equal to $\displaystyle 0.2 \cdot 3N = 0.6 N$

Since $\displaystyle N$ is positive and $\displaystyle 0.5 < 0.6$, 

$\displaystyle 0.5N < 0.6N$,

and (B) is greater.

The easiest way to find 42 percent of 5 is to first find 42 percent of 10. 

42 percent of 10 can be calculated by multiplying .42 by 10. This results in 4.2. 

Given that 5 is half of 10, it follows that 42 percent of 5 is equal to half of 4.2. 

Half of 4.2 is equal to 2.1, which is the correct answer. 

To begin, you can set up a proportion:

$\displaystyle \frac{15}{100}=\frac{x}{500}$

When trying to find a percent of a number, convert the percent into a decimal. To do this, divide the percent by 100.

$\displaystyle 15 \div 100 = 0.15$

$\displaystyle 0.15=\frac{x}{500}$

You then multiply 500 by 0.15. Since 500 represents 100% of Katie's cards, multiplying by 0.15 will give you how many cards equal 15% of the total.

$\displaystyle x=500 \times 0.15 = 75$

The result is your answer.

This question asks you to find a percentage of a smaller part of 100. You must first figure out what the smaller part of 100 equals. Since percents are based off of 100, 30% of 100 is the number 30. You must then find 10% of this number.

To do this, multiply 30 times 10%. First, divide the percentage by 100.

$\displaystyle 10\div100 = 0.1$

Multiply the result times 30.

$\displaystyle 30 \times 0.1 = 3$

The new result is your answer.

If Amir gets rid of 20% of his cards, he will only have 80% of his cards remaining afterwards.

$\displaystyle 100 - 20 = 80$

Therefore, we can figure out how many cards Amir will have after selling 20% of his cards by multiplying times 80% since that will be the amount of cards he will have left, compared to the original number.

To do this, first divide the percentage by 100.

$\displaystyle 80 \div100 = 0.8$

Then, multiply the result of this times 60.

$\displaystyle 60 \times 0.8 = 48$

The result is your answer.

In order to figure out what 60% of 120 is, multiply 60% by 120. To do this, first divide your percentage by 100.

$\displaystyle 60 \div 100 = 0.6$

Then, multiply the result times 120.

$\displaystyle 120 \times0.6 = 72$

The new result is your answer.

The question asks you to find 75% of a smaller part of 48. In order to figure this out, you must first figure out what the value of the smaller part is. To figure out what 25% of 48 is, multiply 48 by 25%. First, divide the percentage by 100.

$\displaystyle 25\div100 =0.25$

Then, multiply 48 by the result.

$\displaystyle 48 \times0.25 = 12$

The second part of the question asks you to figure out what 75% of this new number is. Just like before, first divide the percentage by 100.

$\displaystyle 75\div100=0.75$

Then, multiply the result times 12.

$\displaystyle 12 \times0.75 = 9$

The result is the answer.