An instructor gives an exam with fifteen questions. Students are allowed to choose any eleven to answer. Required:
a. How many different choices of eleven questions are there?
b. Suppose seven questions require proof and nine do not. How many groups of eleven questions contain five that require proof and six that do not?

a. There are 1365 choices of eleven questions.

b. 1764 groups of eleven questions contain five that require proof and six that do not.

Step-by-step explanation:

The order in which the questions are chosen is not important, which means that the combinations formula is used to solve this question.

Combinations formula:

is the number of different combinations of x objects from a set of n elements, given by the following formula.

a. How many different choices of eleven questions are there?

Eleven questions from a set of 15. So

There are 1365 choices of eleven questions.

b. Suppose seven questions require proof and nine do not. How many groups of eleven questions contain five that require proof and six that do not?

5 from a set of 7 and 6 from a set of 9. So

1764 groups of eleven questions contain five that require proof and six that do not.

p ÷ r = tan(x)

step-by-step explanation:

given that there is a figure below shows a right triangle: a right triangle is shown with hypotenuse equal to q units and the length of the legs equal to p units and r units.

graph is missing so i will create the graph as per given information.

the angle between the legs having lengths p units and q units is y degrees. the angle between the legs having lengths r units and q units is x degrees.

now we need to find about what is p ÷ r equal to.

so we can use trigonometric ratio tan(x)=[altitude]/[base] to find the value of p ÷ r, because p is the altitude and r is the base.

p ÷ r=tan(x)

hence final answer is p ÷ r=tan(x).