kelly has a collection of red and blue marbles. The ratio o red to blue marbles is 3 : 7. She has 80 marbles

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To find out the number of red and blue marbles in Kelly's collection, let's break down the problem step by step:

Step 1: Determine the total number of parts in the ratio
The ratio of red to blue marbles is given as 3:7, so the total number of parts is 3+7=10.

Step 2: Calculate the value of each part
Since Kelly has a total of 80 marbles, we can divide this by the total number of parts in the ratio to find the value of each part.
80 / 10 = 8

Step 3: Determine the number of red marbles
Since the ratio of red to blue marbles is 3:7, and each part represents a value of 8, we can multiply the value of each part by the number of parts for red marbles.
3 * 8 = 24 red marbles

Step 4: Determine the number of blue marbles
Following the same logic, we can calculate the number of blue marbles by multiplying the value of each part by the number of parts for blue marbles.
7 * 8 = 56 blue marbles

Therefore, Kelly has 24 red marbles and 56 blue marbles in her collection.