Two rectangles are similar. If their dimensions are 4 by 5 and y and 5, find the value fo y > 5
4 coins are labled as 2, 3, 4 and 5. When 2 coins are drawn without looking, what is the probability that their sum is greater than 8?
Let:
$\displaystyle L_{1} = 4$
$\displaystyle W_{1} = 5$
The ratio between $\displaystyle L_{1}$ and $\displaystyle W_{1}$ is $\displaystyle \frac{5}{4} $
Then:
$\displaystyle L_{2} = 5$
$\displaystyle W_{2} = \frac{5}{4} \times 5 = \frac{25}{4} = 6,25$
So we have to draw coins 4 and 5.
The probability of drawing 4 is $\displaystyle \frac{1}{4}$
The probability of drawing 5 is $\displaystyle \frac{1}{3}$
Multiply the events.
Probability that sum is greater than 8: $\displaystyle \frac{1}{12}$
(By the way, if you draw the 5 first, its probability will be $\displaystyle \frac{1}{4}$, and of course the probability of drawing a 4 would then be $\displaystyle \frac{1}{3}$.