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Independent X,Y have variances t and 2. Find Var(X+Y).

Read the idea, work independently, then explain what changed.

TOPIC 01

Random variables and distributions: mixed review

A mixed assessment: identify the method, justify it and revise your reasoning.

Use one hint at a time. A correction explains what changed, not just the final answer.

01 / Transfer#Your turn

t=32

Variance is nonnegative; variance of a sum includes covariance unless independence is justified.

Skills and prerequisite lessons

Working and explanation

BUILD THE REASONING

Hint 1

List the possible values and probabilities before computing moments.

Hint 2

Use this intermediate relation.

Var(X+Y)=Var(X)+Var(Y)

Worked solution

The requested value is 34.

Checks and common pitfalls: Independence supplies zero covariance here.

Think first. Reveal a hint when the class is ready.

Teacher preparation and assessment