Matt got a dollar on his birthday. On his second birthday he will get the amount from last year's birthday plus as many dollars as he is old. How much would he receive on his birthday when 12 if this pattern is used. I came up with $78 is this right

I will assume you meant, on his first birthday

1st birthday ---- 1
2nd ------------ 1 + 2 = 3
3rd ------------- 3+3 = 6
4th ------------- 6+4 = 10
5th ------------- 10+5 = 15
.....

this is a special sequence called the triangular numers, take a look how billiard balls
would be racked up in the triangle.

sum(n) = n(n+1)/2
so when n=12
sum(12) = 12(13)/2 = 78

You are right
How did you get your answer ?

We did this

1 1
2 3
3 6
4 10
5 15
6 21
7 28
8 36
9 45
10 55
11 66
12 78

To find out how much Matt would receive on his 12th birthday using the given pattern, we need to calculate the amount he receives each year and add them up.

Based on the pattern, on the first birthday, Matt received $1. On his second birthday, he would receive last year's amount, which is $1 plus his age, which is 2. Therefore, on his second birthday, Matt would receive $1 + $2 = $3.

To calculate the amount Matt receives on his subsequent birthdays, we need to continue the pattern:
- On his third birthday, he would receive last year's amount ($3) plus his age (3). So he would receive $3 + $3 = $6.
- On his fourth birthday, he would receive last year's amount ($6) plus his age (4). So he would receive $6 + $4 = $10.
- This process continues, and on his 12th birthday, he would receive last year's amount ($55) plus his age (12). So he would receive $55 + $12 = $67.

Therefore, according to the pattern, Matt would receive $67 on his 12th birthday, which is different from the $78 you mentioned. Double-check your calculations to verify whether $78 is correct or if you made an error along the way.