How many positive integers less than 20 ar?

Question

How many positive integers less than 20 are either a multiple of 2, an odd multiple of 9, or the sum of a positive multiple of 2 and a positive multiple of 9?

Answer 1

A = {2,4,6,8,10,12,14,16,18}

B = {9}

C = {13,15,17,19}

9+1+4=14

Answer 2

if you will include 20, there are 20 positive integers and all positive integers are whole number! all positive integers are numbers that are not negative!! If you will not include 20, there will only be 19.

Answer 3

I may be able to help you. From 0 to 20, no. of integers = 20.

Half of them are even and half odd. Evens are multiples of 2. There are no ways of finding the others. (Do you really want an answer or are you testing our knowledge?)

Answer 4

1. Numbers which are multiples of 2 are even numbers which can be represented by: 2n, where n is an integer which corresponds to the number  of terms. Thus for the numbers from 1 to 19(less than 20)

2n = 19

n = 19/2 int. = 9

2. Numbers which are multiples of 9 can e represented by 9n where n is an integer which corresponds to the number of terms. Thus

9n = 19

n = 19/9 int = 2

3. The sum of an arithmetic series is given by:

Sn = (n/2)(A1 + An)

Where:

n = the number of terms

A1 = the first term in the series

An = the last term in the series

For the multiples of 2 where n = 9, A1 = 2x1 = 2, An = 2 x 9 = 18

Sn = (9/2)(2 + 18) = 90

3. For the multiples of 9 where n =2,  A1=9, An = 18

Sn =( 2/2)(9 + 18) = 27

Answer 5

Multiple of 2: 2, 4, 6, 8, 10, 12, 14, 16, 18

Odd multiple of 9: 9

Sum of 2n and 9m: 11, 13, 15, 17, 19

Count: 15