The first two terms of an arithmetic sequence are a1 = 2 and a2 = 4. What is a10, the tenth term?

Question

A. 10
B. 18
C. 19
D. 20

Answer 1

a = 2; therefore, a10 = 20

Answer 2

a1 = 2
a2 = 4
a3 = 6
a4 = 8
a5 = 10
Now, the rest is simple! 5 doubled is 10, 10 doubled is twenty. So it's D. 20.

OR
a x 1 = 2 , 2 x 1 = 2 then a x 2 = 4 , 2 x 2 = 4 , so if a = 2 then 2 x 10 = 20! Again it's D) 20

Answer 3

Here first term =a1= 2
and second term =a2=4
Therefore Common Difference=d = a2-a1=4-2=2
Using the formula of arithmetic sequence aN=a1 +(n-1)d
a10=2+(10-1)2
= 2 +18
=20

Answer 4

In an arithmetic sequence, the difference between each of the sequential terms is a constant.
a1, a1+d,a1+2d, etc and the n'th term is
a1+(n-1)*d

In this case the difference is d = 2 and the first term is also 2 so the 10'th term would
2+(10-1)*2 = 20


Doug

Answer 5

Since a*1=2 and a*2=4 then "A" is equal to 2. Then a*10 will equal to 20.
So the answer is D. 20

Answer 6

Like another poster, my first inclination was to an exponential progression (1024). But given the multiple choice I'll go with D final answer.

Answer 7

20 .... try it this way:

a1 2
a2 4
a3 6
a4 8
a5 10
a6 12
a7 14
a8 16
a9 18
a10 20

Answer 8

an = a1 + (n - 1)d

a(10) = 2 + (10 - 1)(2)
a(10) = 2 + (9 * 2)
a(10) = 2 + 18
a(10) = 20

ANS : D.

Answer 9

Id say 1024, but i suppose it could be 20 aswell.

Answer 10

is this a trick question? of course it's 20.