Chris finds a mass of 47/100 gram for a rock sample. dana finds a mass of 3/10 gram for his sample. use fractions feom the list to complete an equation and find the total mass of both samples. 3/10, 4/10, 7/10, 3/100, 30/100, 40/100, 47/100, 50/100, 77/100

So when adding fractions your goal is to match the denominators. By this I mean you want to have the same number on the bottom for both fractions. So when adding, you cannot take away from 47/100, you can only add on to 3/10.
So here's a little help;

47/100 + 3/10 

Now we are going to work with 3/10, our goal is to get 10 to match with 100. Meaning we multiply it by 10.
Now we have this:

47/100 + 3/100

But what ever you do to the bottom you must do to the top. So now you multiply 3 by 10 and now you have this:
47/100 + 30/100

Now we can simply just straight up add these.

47/100 + 30/100 = 77/100.

And there's your answer. I hope that helped.

21/2 or 5/2