.. List the 15th
and 19th
triangular numbers.

See below in bold.

Step-by-step explanation:

The formula is Tn = n(n + 1) / 2

The first triangular number is 1(1+1) / 2 = 2/2 = 1.

So the 15th = 15(15+1) / 2 = 120.

and the 19th = (19 * 20) / 2 = 190.

15%

step-by-step explanation:

use the table and count the number of guesses that has two correct answers.

the following are two correct answers

10010, 01100, 11000

a total of 3 numbers having 2 correct guesses out of 20 questions.

probability of getting 2 correct guesses = the number of questions getting 2 correct answers / total number of questions.

= 3/20

to convert it into percent multiply by 100, we get

= 3/20 * 100

= 15%

the answer is 15%

you.