4th grade math
posted by Will .
A store clerk wants to stack 55 cans of tennis balls in a triangular display. How many cans would be in the bottom row?

answer is 10...i used guess and check ...!

We also got ten, but we trying to explain it to a 9 year old for her schoolwork. That is where we are stuck.

i need help on fact families 6 and 5 pleaseeeeee answer me

Estimating Products Example 7multiply42 is close to 7 multiply ?

Math is the study of patterns.
My first column is the sum of cans after so many rows,
the second column in the increase in the number of cans
Think of racking up billiard balls
.......О
.....О О
....О О О
...О О О О
..О О О О О
.О О О О О О
О О О О О О О
О О О О О О О О
1
2
3
3
6
4
10
5
15
6
21
etc, do you see the pattern? 
10

the answer i got was 7 tennis balls

There are 8 pencils in a package how many packages will be needed for 28 children if each child gets 4 pencils