Distribution of sum of two uniform random variables

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Suppose $X$ is uniformly random on $[0, 1]$, $Y$ is uniformly random on $[1, 2]$, and $X$ and $Y$ are independent. I was asked on an interview to find the distribution of $Z=X+Y$. I know how to do this by integrating the joint PDF, but I believe there should be a quicker graphical way. What is the cleanest way to see the result?

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The sum of continuously uniform variables is a bit like the sum of discretely uniform ones. Visualise the histogram for the sum of two standard die: you probably know it's a triangle, peaking in the middle. So for your problem, you want a triangle peaking at $0.5+1.5=2$, its base running from $1$ to $3$. Unitary gives the height as $1$.