Answer:
30 red marbles
Step-by-step explanation:
If the ratio is 2 red marbles for every 5 blue marbles then you would add them together to find out how many marbles are in one group.
2+5=7
There are 7 marbles in each group.
Now we have to find out how many total groups there are by dividing the total amount of marbles by the amount in each group.
105÷7=15
There are 15 groups of 7 marbles.
Looking back at the ratio, we know that the 15 groups each have 2 red marbles and 5 blue marbles. So if there is 2 red marbles 15 times (2 marbles in 15 groups) we would multiply.
2×15=30
There are 30 red marbles.
I hope that makes sense.
