combining random variables

Review combining random variables for AP Statistics and try 1 free AP-style practice question. 17 questions on this topic in AP Statistics · Unit 4 · Probability, Random Variables, and Probability Distributions.

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Question 1

A bakery's daily flour use $X$ has mean 24 kilograms and standard deviation 4 kilograms, and its daily sugar use $Y$ has mean 18 kilograms and standard deviation 6 kilograms. The two quantities are independent of each other. Which of the following is closest to the standard deviation of the total daily use $X + Y$ ?

16 more questions on this topic

Full practice for AP Statistics · Unit 4 · Probability, Random Variables, and Probability Distributions: timed tests, step-by-step explanations for every answer, and AI grading for free-response questions.

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Answer, then see why

The price of gasoline rises 10% and the quantity demanded falls 5%. What happens to total revenue?

Not quite. The answer is B.

Why the other options are wrong

AI grading for free-response

Write your FRQ answer and get it scored point by point against the AP rubric, with the line from your answer that earned or missed each point.

Question 13 / 4 pts

Part a1 / 1 pts

Point 1: Earned

94% sure

Reason: Correctly identifies demand for gasoline as inelastic.

Evidence: "The price of gasoline rises and the quantity falls only a little."

Part b2 / 3 pts

Point 1: Earned

91% sure

Reason: Graph shows relatively inelastic demand.

Evidence: Draws a steep demand curve.

Point 2: Earned

88% sure

Reason: Correct new equilibrium price.

Evidence: Shifts supply left, P1 → P2.

Point 3: Not earned

82% sure

Reason: With inelastic demand, a price increase raises total revenue.

Evidence: "Revenue goes down."