The normal cost of a chair is $27.00. A man purchased the chair using a coupon for 25% off. How much did he pay for the chair?

Some people think it is unlucky if the 13th day of month falls on a Friday. show that in that there year (non-leap or leap) ther

Vlad1618 [11]

<span>There are several ways to do this problem. One of them is to realize that there's only 14 possible calendars for any year (a year may start on any of 7 days, and a year may be either a leap year, or a non-leap year. So 7*2 = 14 possible calendars for any year). And since there's only 14 different possibilities, it's quite easy to perform an exhaustive search to prove that any year has between 1 and 3 Friday the 13ths. Let's first deal with non-leap years. Initially, I'll determine what day of the week the 13th falls for each month for a year that starts on Sunday. Jan - Friday Feb - Monday Mar - Monday Apr - Thursday May - Saturday Jun - Tuesday Jul - Thursday Aug - Sunday Sep - Wednesday Oct - Friday Nov - Monday Dec - Wednesday Now let's count how many times for each weekday, the 13th falls there. Sunday - 1 Monday - 3 Tuesday - 1 Wednesday - 2 Thursday - 2 Friday - 2 Saturday - 1 The key thing to notice is that there is that the number of times the 13th falls upon a weekday is always in the range of 1 to 3 days. And if the non-leap year were to start on any other day of the week, the numbers would simply rotate to the next days. The above list is generated for a year where January 1st falls on a Sunday. If instead it were to fall on a Monday, then the value above for Sunday would be the value for Monday. The value above for Monday would be the value for Tuesday, etc. So we've handled all possible non-leap years. Let's do that again for a leap year starting on a Sunday. We get: Jan - Friday Feb - Monday Mar - Tuesday Apr - Friday May - Sunday Jun - Wednesday Jul - Friday Aug - Monday Sep - Thursday Oct - Saturday Nov - Tuesday Dec - Thursday And the weekday totals are: Sunday - 1 Monday - 2 Tuesday - 2 Wednesday - 1 Thursday - 2 Friday - 3 Saturday - 1 And once again, for every weekday, the total is between 1 and 3. And the same argument applies for every leap year. And since we've covered both leap and non-leap years. Then we've demonstrated that for every possible year, Friday the 13th will happen at least once, and no more than 3 times.</span>

5 0

3 years ago

What substitution should be used to rewrite 4x^4-21x^2+20 =0 as a quadratic equation

marysya [2.9K]

I would substitute y = x^2

4y^2 -21y+20=0

7 0

4 years ago

What percentage is .0019951

ICE Princess25 [194]

The most exact answer would be 0.19951% but the approximate answer would be 0.2%.

8 0

3 years ago

Read 2 more answers

Of 100 students,65 are members of a mathematics club and 40 are members of a physics club. if 10 are members of neither club the

alexandr1967 [171]

a. 15 students are members of both clubs

b. 50 students only are members of the mathematics club

c. 25 students only are members of the physics club

Step-by-step explanation:

The given is:

There are 100 students
65 are members of a mathematics club
40 are members of a physics club
10 are members of neither club

We need to find how many students are members of

a. both clubs?

b. only mathematics club

c. only physics club

∵ The total number of students = 100

∵ 10 are members of neither club

- Subtract 10 from 100 to find the members of the mathematics

club or the physics club

∵ 100 - 10 = 90

∴ There are 90 members of the mathematics club or physics club

∴ n(mathematics or physics) = 90

∵ 65 students are members of a mathematics club

∵ n(mathematics) = 65

∵ 40 students are members of a physics club

∴ n(physics) = 40

∵ n(mathematics or physics) = n(mathematics) + n(physics) - n(both)

∴ 90 = 65 + 40 - n(both)

∴ 90 = 105 - n(both)

- Add n(both) to each side

∴ n(both) + 90 = 105

- Subtract 90 from each side

∴ n(both) = 15

∴ 15 students are members of both clubs

a. 15 students are members of both clubs

∵ 65 students are members of the mathematics club

∵ 15 of them are members of the physics club

∴ n(mathematics only) = 65 - 15 = 50

∴ 50 students only are members of the mathematics club

b. 50 students only are members of the mathematics club

∵ 40 students are members of the physics club

∵ 15 of them are members of the mathematics club

∴ n(physics only) = 40 - 15 = 25

∴ 25 students only are members of the physics club

c. 25 students only are members of the physics club

Learn more:

You can learn more about word problems in brainly.com/question/8907574

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5 0

3 years ago

Anyone know what the answer is

Mars2501 [29]

Answer:

22,-15 ................ maybe

4 0

3 years ago