Answer:
hrs/house
Step-by-step explanation:
Rate is the amount of work done per unit of time;
Let Cara's rate = C
Let Jena's rate = J
C + J = 4 ------ i
Now;
Working alone:
Jena takes twice as long as Cara
J = 2C ---- i
How long does it take Cara to clean a house alone
C + J = 4
J = 2C
C + 2C = 4
3C = 4
C = hrs/house
Answer:
a) 1,757,600 different plates possible.
b) 1,404,000 different plates possible.
Step-by-step explanation:
The permutations formula is important to solve this question.
Permutations formula:
The number of possible permutations of x elements from a set of n elements is given by the following formula:
(a) can be repeated:
There are 3 letters, each one with 26 possible outcomes.
2 digits, each with 10 possible outcomes
So
T = 26*26*26*10*10 = 1757600
1,757,600 different plates possible.
(b) cannot be repeated:
Here the permutations formula is used.
Three letters, from a set of 26.
Two digits, from a set of 10. So
1,404,000 different plates possible.