Total number of trees n = 4 + 3 + 3 = 10. Count the number of each different trees. n1=4, n2=3, n3=3. Number of ways the landscaper plant the trees in a row is = 10 ! / ( 4! * 3! * 3! ) = 3628800 / ( 24 * 6 * 6 ) = 3628800 / 864 = 4200 ways.
Therefore, the trees can be planted 4200 ways
Given:
Total number of cubes = 40
Red cubes = 18
Blue cubes = 13
Yellow cubes = 9
Aysha adds some more red cubes into the bag.
The probability now that she will take a red cube is 0.5.
To find:
The probability that she will take a yellow cube.
Solution:
Let Aysha adds x red cubes into the bag. Then,
Number of total cubes = 40+x
Number of red cubes = 18+x
Probability of getting a red cube is:

The probability now that she will take a red cube is 0.5. So,





Divide both sides by 0.5.


It means Aysha adds 4 more red cubes into the bag.
Now, the total number of cubes int he bag is:

Probability of getting a yellow cube is:


Therefore, the required probability is
.