Each marble bag sold by tammy's marble company contains 5 blue marbles for every 3 green marbles....

Question:

Each marble bag sold by tammy's marble company contains 5 blue marbles for every 3 green marbles. if a bag has 21 green marbles, how many blue marbles does it contain?

Ratio and Proportion

Ratios can be expressed into fractions. When two fractions are equivalent, then the two ratios form a proportion. A proportion may be created by multiplying both the terms of a ratio by a factor called the scale factor.

Answer and Explanation:

If the ratio of blue to green marble is 5:3, we have:

{eq}\dfrac{5}{3} = \dfrac{b}{21} {/eq}

where b is the number of blue marbles.

Solving for b, we will have:

{eq}\begin{align} \dfrac{5}{3}& = \dfrac{b}{21}\\[0.2cm] \,&\,\Downarrow\\[0.2cm] \dfrac{5}{3}(21)& = b\\[0.2cm] \dfrac{105}{3}&=b\\[0.2cm] b&=35 \end{align} {/eq}

Therefore, there are 35 blue marbles.


Learn more about this topic:

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Calculations with Ratios and Proportions

from ELM: CSU Math Study Guide

Chapter 2 / Lesson 13
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