number Series problem ..... need answer >asap<

You just have to findout 1st 13 prime numbers.

1st prime number is 2 and 2nd is 3 so 1 + 2 = 5 (2 + 3).

3rd is 5 and 4th is 7 then 3 + 4 = 12 ( 5 + 7).

And next same like this.

Prime series : [ 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61 ]

so answer is 10 + 13 = (29+41)=70

The second one is the Fibonacci Series......0,1,1,2,3,5,8,13,21,34,55,89,144.......

The nth term ...starting with the second term (0 is the 0th term) is just the sum of the previous two

The nth term ( Fibonacci Number) is given by

F(n) =  [ (1 + √5 )ⁿ -  (1- √5 )ⁿ ] / (2ⁿ√5)

F(20) = 6765

Dear cphill,

what about 1st problem ??

Let's assume that we have an arithmetic series here (I don't know if we do, or not)

An arithmetic series is given by

a_n+1 = a_n + (n-1)d

Where a_n+1 is the term following a₁.....n represents the nth term of the series, and d is the common difference between successive terms

Let's call the first term a₁. And the second term(a₂) is just a₁ + (2-1)d = a₁ + d

So the sum of the first two terms is just

a₁+ (a₁ + d) = 5   or     2a₁ + d = 5    .....call this Equation 1

And the third term (a₃) is just ....  a₁ + (3-1)d =   a₁ + 2d

And the fourth term(a₄) is just.....    a₁ + (4-1)d  = a₁ + 3d

And the sum of these two terms = 12...... so

a₁ + 2d + a₁ + 3d  = 12    or    2a₁ + 5d = 12   ......     call this Equation 2

Now multiplying Equation 1 through by -1 on both sides and adding it to Equation 2, we get

4d = 7      so d = 7/4

And substituting for d in Equation 1, we have

2a₁ + 7/4 = 5

2a₁ = 13/4

a₁ = 13/8   and that's the first term.....Now, lets check our results

a₂ = a₁ + (2-1)(7/4)  = 13/8 +7/4  =  27/8

So    a₁ + a₂= 13/8 + 27/8 = 40/8 = 5  .....and that's OK

And the sum of a₃ and a₄  is given by Equation 2 = 2a₁ + 5d = 12

So we have

2(13/8) + 5(7/4) =

26/8 + 35/4 =

26/8 + 70/8 =

96/8  =   12     .....and that's OK, too

So our series (so far) is just

13/8, 27/8,  41/8,  55/8

And the sum of the 10th and 13th terms is

[a₁ + (9)d] + [a₁ + (12)d] = 2a₁ + 21d =  2(13/8) + 21(7/4) =  26/8 + 294/8 = 320/8 = 40

Hey chris dosent your fingers get tired!!!!???Lol

You don't know the half of it, zegroes....I spent all afternoon helping a girl with an Algebra 2 Test and a Trig Test...........

In short....I'm fried !!!!

Ah....your answer was certainly "easier," Anonymous!!!.......but mine was  pretty interesting, too........if I do say so myself !!!