A monument is built out of toothpicks. There are 30 rows and each row has seven more toothpicks than the row above. The top row has five toothpicks.

Part 1: How many toothpicks are on the bottom row?

Part 2: Using complete sentences, explain the procedure taken to answer this question.

Question

A monument is built out of toothpicks. There are 30 rows and each row has seven more toothpicks than the row above. The top row has five toothpicks. 

Part 1: How many toothpicks are on the bottom row? 

Part 2: Using complete sentences, explain the procedure taken to answer this question.

johnweldon1993 · Answer

Well not counting the top row....there are 29 rows.... adding 7 each time....so it would be

7 times 29 = 203 toothpicks I believe

jdoe0001 · Answer

heheh, that'd be a small building, is not a good idea to make them off toothpicks btw :)

7 * 29  is 203

but the top row is
            5
         5+7
      5+7+7
    5+7+7+7
.....

anonymous · Answer

im thinkin 208

johnweldon1993 · Answer

Or you can look at the equation

$$a _{n}=a _{1}+(n-1)d$$

'd' is the common difference (7)
n = number of rows you have (30)
and a1 is your first term so


$$a _{30}=5+(30-1)7$$

Right @physicsboffin

anonymous · Answer

LOl @johnweldon1993

johnweldon1993 · Answer

Which does come out to 208

anonymous · Answer

a+29d=5
d=-7
a=29(7) +5
=208

cwrw238 · Answer

the formula for the nth term is a + (n - 1)d

where a = first term,  d = common difference

cwrw238 · Answer

so the bottom term which is 30th is

5 + (30 - 1)*7 = 5 + 203 = 208