First, we need to determine the percentage of cats that are grey. To do this, we subtract . Therefore, 68% of cats are grey.

The quick estimation method allows us to compute this problem quickly and save time on later questions. To begin, we need to determine 10% of the total amount of cats. In order to find 10% of a number, simply move the decimal point one place to the left. So, 10% of 300 cats is 30 cats. 

We want to determine how many cats constitute 68% of the total amount of cats. 68% can be rounded to 70% in order to estimate and find the closest answer choice. 70% is 7 times 10% so all we need to do is multiply 10% (30 cats) by 7. Therefore,

 are orange. 

Now, look at the answer choices and choose the one closest to your estimation. Keep in mind that we over estimated, so the answer you choose should be slightly less.

One way to solve this problem is to use cross multiplication. 

So in order to determine the number of green birds, set this proportion equal to.

Therefore, 

Cross multiply to get

. Now divide both sides of the equation by 100 to get

A faster way to solve this problem is to recognize that 100 and 1000 differ by only one decimal place (1000 has an extra zero). Therefore, in order to determine 68% of 1000, simply add an extra zero to 68 and you have 680 birds. 

First, we need to determine the percentage of snacks that are unhealthy. To do this, we subtract 

 Therefore, 30% of snacks are unhealthy.

The quick estimation method allows us to compute this problem quickly and save time on later questions. To begin, we need to determine 10% of the total amount of snacks. In order to find 10% of a number, simply move the decimal point one place to the left. So, 10% of 500 snacks is 50 snacks.

We want to determine how many snacks constitute 30% of the total amount of snacks. 30% is 3 times 10% so all we need to do is multiply 10% (50 snacks) by 3. Therefore,

 are unhealthy.

To calculate the tax, multiply 8.5%. or, equivalently, 0.085, by $139.34, rounding to the nearest cent:

Add the tax to the price before tax:

The amount paid will be $151.18.

The total number of plants has to be divisible by 3.  Of the answer choices, the only one that is divisible by 3 is 18.  You can check this because numbers that are divisible have the sum of their digits also divisible by 3. For example,

which is divisible by 3, so 18 is divisible by 3.

330 is 75% of a number we will call ; alternatively, 0.75 multiplied by  is equal to 330. Set up this equation and solve for :

We can rewrite  % as 12.5%. 88 is 12.5% of a number , or, equivalently, 0.125 multiplied by a number  is equal to 88. We can write this as an equation and solve for :

We can rewrite  % as 2.5%. 32 is 2.5% of a number , or, equivalently, 0.025 multiplied by a number  is equal to 32. We can write this as an equation and solve for :

3% of 5,319 can be calculated by multiplying 5,319 by 0.03, the decimal equivalent of 3%:

Multiply 5,319 by 3, then move the decimal point so that two digits are to the right:

,

so

Rounded to the nearest whole number, this is 160 signatures.

Set up the proportion statement and solve for  by cross-multiplying: