How many students have used all three modes of transportation? solution please

Complete question is;

In a class of 40 students, 17 have ridden an airplane, 28 have ridden boat, 10 have ridden a train, 12 have ridden an airplane and a boat, 3 have ridden a train only, and 4 have ridden airplane only. Some students in the class have not ridden any of the three modes of transportation and an equal number have taken all three. How many students have used all three modes of transportation?

4 students

Step-by-step explanation:

Let the number of students who used airplane be A

Let the number of students who used boat be B

Let the number of students who used train be C

Now, we are told that 17 rode plane.

Thus; A = 17

28 rode boat; B = 28

10 rode train; C = 10

12 rode airplane and boat; A ∩ B = 12

4 rode plane only; A' = 4

3 rode boat only; C' = 3

Total number of students; T = 40

Now, total number of students is represented by;

T = A - B - C - (A ∩ B) - (B ∩ C) - (C ∩ A) + (A ∩ B ∩ C)

We don't have (B ∩ C) and (C ∩ A).

Now, the can be derived from the expression of C' which is;

C' = C - (B ∩ C) - (C ∩ A)

C' = C - [(B ∩ C) + (C ∩ A)]

We are given C' = 3 and C = 10

Thus;

3 = 10 - [(B ∩ C) + (C ∩ A)]

10 - 3 = [(B ∩ C) + (C ∩ A)]

7 = [(B ∩ C) + (C ∩ A)]

Rearranging the total number of students equation, we now have;

T = A - B - C - (A ∩ B) - [(B ∩ C) + (C ∩ A)] + (A ∩ B ∩ C)

Where;

(A ∩ B ∩ C) is the number of students that used all three modes of transportation.

Thus, plugging in the relevant values;

40 = 17 + 28 + 10 - 12 - 7 + (A ∩ B ∩ C)

40 = 36 + (A ∩ B ∩ C)

(A ∩ B ∩ C) = 40 - 36

(A ∩ B ∩ C) = 4

b. an equilateral triangle inscribed in a circle

step-by-step explanation:

we are given the figure of two circles having a triangle inside.

now, we know that,

"when a figure is lying inside an another figure, then the outside figure is known as circumscribed figure and the figure lying inside is referred to as the inscribed figure".

as we see that, the circles are containing the triangle completely.

thus, the circles are the circumscribed figures and the triangle is the inscribed figure.

hence, we get, 'an equilateral triangle is inscribed in a circle'.

answer: this is not a question

step-by-step explanation: this is a answer