If there are 5 terms, the first is 2 and the last term is 4, find the common difference.

0.5

Step-by-step explanation:

Let's imagine the terms like this:

2, ?, ?, ?, 4

Pretend they're on a number line, then use the guess and check method. We know that the number must be less than 1, because there are 4 tics between 2 and 4 (including 4's tic) and 2 + 4 is not equal to 4. We know that it is greater than 0 because 2 and 4 are both positive. Using this logic, try 0.5. Add 0.5 to 2, the term after 2, and so on.

2, 2.5, 3, 3.5, 4

It is valid, therefore the common difference is 0.5.

what is the original number? you forgot to add it.

a 4/6 = 9/12   not proportional

step-by-step explanation:

to find which are not proportional, we can use cross products

if it is true, they are proportional.   if it is not true, they are not proportional.

a 4/6 = 9/12

4* 12 = 6*9

48 = 54

not this is not proportional  

b 2/3 = 12/18  

2* 18 = 3 * 12

36 = 36

this is proportional

c 5/4 = 10/8  

5*8 = 4*10

40 = 40

this is proportional

d 7/5 = 35/25

7*25 = 5 * 35

175 = 175

is proportional