You have some marbles. When you make a shape of an equilateral triangle, you either have 4 extra, or you need 28 more to complete the shape. How many marbles do you have? How long is a side of the biggest equalateral triangle that you can make make with your marbles?

You have 500 marbles.

The longest side of the biggest equalateral triangle that you can make with your marbles is 31

Step-by-step explanation:

28 + 4 = 32

So our equation is:

TR(32) - 28

Now find Triangular Number 32: (32 *33)/2=528

528 - 28 = 500

So, we have 500 marbles

Now we need to find the longest side of the biggest equalateral triangle that you can make make with your marbles

Let's go back to 28 + 4 = 32

One row above 32 is 31

So the longest side of the biggest equalateral triangle that you can make with your marbles is 31

Hope this helps!

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step-by-step explanation: