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 using a table.
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?
Check for Understanding
Ratio
White to
Brown Eggs
Decimal
Fraction
Percentage