Bluebook SAT Test Linear Functions 14

Question 1

The equation y = −4x + 20 represents the remaining battery percentage of a phone x hours after charging stops. When will the battery reach 0%?

Accepted Answer

5 hours

Answer

0 = −4x + 20 → 4x = 20 → x = 5.

Question 2

Two lines are defined by y = 2x + 5 and y = 2x − 3. Which of the following is true?

Accepted Answer

They are parallel and never intersect

Answer

Both have slope 2 but different y-intercepts (5 and −3), so they are parallel.

Question 3

A linear function f has the property that f(x + 2) − f(x) = 10 for all x. What is the slope of f?

Accepted Answer

5

Answer

f(x+2)−f(x) = m(x+2)+b−(mx+b) = 2m = 10 → m = 5.

Question 4

The data below models a linear pattern. What is the missing y value?
x: 3, 6, 9, 12 | y: 7, 13, 19, ?

Accepted Answer

25

Answer

Rate of change = (13−7)/(6−3) = 2; y increases by 6 every 3 units in x; y at x=12 is 19 + 6 = 25.

Question 5

A caterer charges $200 as a flat fee plus $35 per guest. A client has a budget of $900. What is the maximum number of guests g they can invite?

Accepted Answer

20

Answer

200 + 35g ≤ 900 → 35g ≤ 700 → g ≤ 20.

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