Question

Jamila is making a triangular wall with building blocks. The top row has one block, the second row has three, the third has five, and so on. How many rows can she make with a set of 100 blocks?

Answer 1

well this is arithmetic series

Answer 2

what is a1, d , an ?

Answer 3

i thoguht it was pascal's triangle

Answer 4

or is pascals an arithmetic series?

Answer 5

you can solve it using arithemetic series sum ..
lets go with it .. a1 , d , an can you find them ?

Answer 6

an would be 100 yes? a1 would be 1 and d would be 2 i think.

Answer 7

by an i mean general term

Answer 8

an = a1 + (n-1)d

Answer 9

Oh, i'm clueless on an then :/

Answer 10

i'll just take numbers and plug them in though, thanks for equation :)

Answer 11

d=2,a1=1
an = 1 + (n-1)*2 = 2n - 1
Sn = n * (an + a1) / 2
n * (2n - 1 + 1) / 2 = 100
200 = 2n^2
n = 10

Answer 12

look at it

Answer 13

Sn -> sum of n terms

Answer 14

so Sn= 1+(9)2..so 19?

Answer 15

what i wrote up there is the whole solution..
first i found the general term formula (an)
for example an(1) = a1 an(2) = a2 etc
then i used
Sn = n * (an + a1) / 2
this formula gives you the sum of "n" terms
we only have 100 blocks so we need this sum to be 100
and we are looking for n -> number of rows
plugging an,a1 into this formula
gives you n = 10

Answer 16

oh dang lmao. my bad dude thanks :)

Answer 17

yw;)