The term "closed" in math means that if you take two items from a set, do some operation, then you'll always get another value in the same set (sometimes you may get the same value as used before). For example, adding two whole numbers leads to another whole number. We therefore say "the set of whole numbers is closed under addition". This applies to integers as well because integers are positive and negative whole numbers. So we can say that integers are closed under addition.
Integers are not closed under division. Take two integers like 2 an 5 and divide: 2/5 = 0.4 which is not an integer. Integers don't have decimal parts.
The set of whole numbers is {0,1,2,3,...} and we can subtract the two values 1 and 2 to get 1-2 = -1. The order matters here. Subtracting a larger value from a smaller leads to a negative. The value -1 is not in the set of whole numbers. So we can say that whole numbers is not closed under subtraction
Finally, the set of irrational numbers is closed under addition. Adding any two irrational numbers leads to another irrational number. For instance, pi+sqrt(2) = 3.142 + 1.414 = 4.556; I'm using rounded decimals as approximate values. An irrational number is one where we cannot write it as a fraction of integers. Contrast that with a rational number in which we can write it as a fraction of integers. Example: 10 = 10/1 is a rational number.
Answer:
Fred would take 33 days to save $ 70.95.
Step-by-step explanation:
The number of days (
) is directly proportional to the quantity of money saved (
), in monetary units, then we can calculate the time taken to save $ 70.95 by simple rule of three:
Fred would take 33 days to save $ 70.95.
3d+ 3s = $21 because they bought three drinks and three snacks
Answer:
a. The Mexican Airline offers a better deal for 9 students to travel.
b. 10 students
Step-by-step explanation:
a. The Mexican Air airline offers a round trip airfare of $250 per person.
So, for 9 students the fare will be total $(250 × 9) = $2250
Now, the Fiesta airline offers a round trip airfare of $150 per person if the club agrees to pay a one-time group rate processing fee of $1000.
So, for 9 students the total fare will be = $[1000 + (150 × 9)] =$2350.
Therefore, the Mexican Airline offers a better deal for 9 students to travel. (Answer)
b. Let for x students both the airline offers the same total costs.
Then we can write
250x = 1000 + 150x {From the conditions given}
⇒ 100x = 1000
⇒ x = 10
So, if the number of students is 10, then only both the airlines will take same fare. (Answer)
4x-2+1=3x+5
Subtract 3x from both sides
x-2+1=5
Same as
x-1=5
Add 1 to both sides
x=6
