Education.com
Try
Brainzy
Try
Plus

# Tip #32 to Get a Top ACT Math Score

By McGraw-Hill Professional
Updated on Sep 7, 2011

The graph of the equation y = mx + b is a line. In the equation, m is the slope, sometimes called the rate of change, and b is the y intercept (the place where the line crosses the y axis). Usually, that is enough to get a question right.

Let's take a look at this question:

Solution: The fee for each bottle, \$20, goes next to x. And \$25 is a fixed fee, unrelated to how many bottles someone buys, so \$25 stands alone: y = 20x + 25.

That was so easy to explain that I have some room left. So, here's Brian's Math Magic Trick #2.

### Easy

1. If a movie trailer offends 45 people in a theater, and then the feature movie disturbs 25 more people every scene the villain appears in, which of the following equations expresses the number of people offended or disturbed after x villain scenes in the movie?
1. y = 45
2. y = 25x + 45
3. y = 20x
4. y = 70x
5. y = 20x + 70
2. ### Medium

3. Which of the following equations best fits the information in the table below?
1. y = 5x – 2
2. y = –9.5
3. y = 2x – 4
1. y = 0.25x + 3
2. y = –9.1x
4. Which of the following equations could represent the graph in the standard (x, y) coordinate plane shown below?
1. y = 2
2. y = 2x + 2
3. y = 4x
4. y = –x + 2
5. y = 4x + 4
5. If the cost of advertising on Facebook consists of a fixed charge plus a charge per insertion of the ad, based on the table below, what is the fixed charge?
1. 1000
2. 976
3. 500
1. 34
2. 33
6. For the first 10 seconds after a geyser erupts, its height is given by h = 3.4s, where h is in feet and s represents seconds after erupting. When will the geyser first be over 20 feet tall?
1. Between 3 and 4 seconds
2. Between 4 and 5 seconds
3. Between 5 and 6 seconds
4. Between 6 and 7 seconds
5. Between 7 and 8 seconds