Write in summation notation?

Question

3+15+75+...+9375.

Can someone please show me how this is done? Many thanks!

Answer 1

5

E 3 x 5 ^i

i=0

E is the summation sign sigma
^i signifies to the power of i

the summation is from 0 to 5

Answer 2

Right away I see a common factor of 3 in 3,15,75 and
with a little in-my-head arithmetic I see that 3 is a factor in
9375 also. Then I see the cofactors of 3 in15 and 75 are
5 and 25 respectively and I start to suspect powers of 5.
In fact 3 has a factor of 5^0 when you think of 3=3X1.
So I analyze 9375 as 3X3125 and 3125 as 5^5. Now I just fill in the blanks and I have

1) 3X5^0 +3X5^1+3X5^2+3X5^3+3X5^4+3X5^5

Then I factor out the 3 and express the remaining as
5^n for n=(0,1,2,3,4,5) and put a Σ in front and n=0 under it and
a 5 over it something like this

---5
--3Σ5^n
----n=0 which means 1) But you write it w/o the dashes,

I had to put them in to preserve the indentation

Answer 3

a number is obtained by multiplying its former by 5

so first 3
after 3*5 =15
after 15*5 =75
after 75*5 =375
after 375*5 =1875
finally 1875 *5 = 9375

add these numbers 3+15+75+375+1875+9375 = 11718

Answer 4

3 x 5 = 15

15 x 5 = 75

75 x 5 = 375

375 x 5 = 1875

1875 x 5 = 9375

- - - - - - -s-

Answer 5

one million. Use summation notation to jot down the sequence 40 9 + fifty 4 + fifty 9 +... for 14 words. answer (C) 2. Use summation notation to jot down the sequence 6.6 + 15.4 + 24.2 +... for 5 words. answer (B)

Answer 6

Every time you add 5 times the current value.

sigma i, where i+1 = 5i, from i=3 to 9375

Sorry it is hard to type out

Answer 7

S = 3* sum ( 5^(i-1), i=1...6)

Answer 8

I don't understand that at all.

Coach