1/4 * 1/3 * 1/2 * 1/1 = 1/24 chance that all 4 letters are placed in the correct envelopes.
With the first envelope, there are 4 choices of letters, so the probability of picking the correct letter is 1/4.
With the second envelope, there are 3 remaining letters, so the probability of picking the correct letter is 1/3.
The same logic follows the the third and final letter.
If two fractions have the same denominators, then just simply add up the numerators together and keep the denominator.
Examples:
Answer:
The perimeter of a rectangle is the sum of both lengths and both widths, which is equal to 54 meters. Let's call Length L and Width W.
The question is saying this: L = 3 meters + 3(W). We have 2 variables, which means we need at least 2 equations to solve. So far we have one, our second equation is from the perimeter.
2 lengths + 2 Widths = 54. Now, it's just a plug and chug.
2(3 + 3W) + 2W = 54.
6 + 6W + 2W = 54
8W = 48
W=6
L = 3 + 3(6) = 21
To double check: 2(21) + 2(6) = 42 + 12 = 54
The Width is 6 meters, and the Length is 21 meters.
