Transcript Document

6.RP Understand the concept of a ratio and use ratio language to
describe a ratio relationship between two quantities.
Ratios
What is a ratio?
A ratio is a comparison of one quantity to
another.
For example if I were baking a cake and
needed to have one part sugar to four parts
flour the ratio would be 1:4 or ¼.
DON’T CONFUSE FRACTIONS WITH RATIOS
The difference between fractions and
ratios
• If we were mixing oil for a two cycle engine it
might call for a 1:50 ratio. This means for every
one part of oil it would be 50 parts gas.
• For the sake of simplicity we will begin with a 1:4
ratio and say that the first number is oil and the
second number is gas.
• How is a 1:4 ratio or ¼ different than saying that
¼ (fraction) or 25% of the gas oil mixture is oil?
Difference between fractions and
ratios continued
• A 1:4 ratio means that there are 5 parts all
together and one part is oil. It can be represented
by ¼. This is why the context of the problem is
important.
Oil
20%
Gas
20%
Gas
20%
Gas
20%
Gas
20%
¼ as a fraction means that there are 4 parts and
25% of them are oil. If you mixed gas using a
fraction model instead of a ratio would you have to
much or to little oil in your mixture?
Oil
25%
Gas
25%
Gas
25%
Gas
25%
Extension
Little Red Riding Hood has a basket that holds
eight eggs. 5 of them are brown and 3 are white.
1. What are all the ratios of eggs? Hint: Think
about comparing all sets, brown, white and
totals.
2. Change all the ratios to fractions, decimals
and percentages.
3. What does each decimal or percentage mean
in relation to the context?
Things to consider
• What mathematical model would help me represent
this?
• An area model?
• A ratio table?
What is the relationship between between decimals and
percentages?
What is the relationship between fractions, decimals and
percentages?
Discuss in groups before answering the question. Start with ½. How
would you express it as a decimal and fraction? How does this help
you to solve the Little Red Riding Hood problem?