You have a box which contains only red marbles and blue marbles. The mass of one red marble is 16 grams, while the mass of one blue marble is 20 grams. If the box contains 21 red marbles and 18 blue marbles, what is the total mass of the marbles in the box?

that would be 21*16 + 18*20 = 696g

the mass of one red marble is 16g and you have 21 red marbles, therefore

16.21=336grams
And you have 18 blue marbles and the mass of one blue marble is 20 grams
therefore, 20.18=360g
336g+360g=696grams total in the box..
I hope my answer is correct.

To find the total mass of the marbles in the box, you need to multiply the number of each color of marbles by their respective masses, and then sum up the results.

Let's calculate the mass of the red marbles first. You have 21 red marbles, and each red marble weighs 16 grams. So the total mass of the red marbles is:

Total mass of red marbles = Number of red marbles * Mass of each red marble
Total mass of red marbles = 21 * 16 grams

Now let's calculate the mass of the blue marbles. You have 18 blue marbles, and each blue marble weighs 20 grams. So the total mass of the blue marbles is:

Total mass of blue marbles = Number of blue marbles * Mass of each blue marble
Total mass of blue marbles = 18 * 20 grams

Now, to find the total mass of the marbles in the box, you need to add the total mass of the red marbles and the total mass of the blue marbles together:

Total mass of marbles in the box = Total mass of red marbles + Total mass of blue marbles

So, you can calculate the answer by substituting the calculated values into the equation:

Total mass of marbles in the box = (21 * 16 grams) + (18 * 20 grams)

Now you can compute the result to find the total mass of the marbles in the box.