BUKSIS-5.1 BARU by prabaarum

VIEWS: 8 PAGES: 5

									5.1
Ali has 9 books, while Lia has 6 books.

What are you going to learn?
To determine proportion To determine proportion of two numbers

I have nine books

I have six books

Key Terms:
proportion ratio

Look at the picture above, and answer the following questions. a) How many books does Ali have? b) How many books does Lia have? The answers are shown in the following table. The number of Ali’s books 9 The number of Lia’s books 6

We can say that the ratio of Ali’s books to Lia’s books is 9 : 6. The above table can also be written as follows: The number of Lia’s books 6 The number of Ali’s books 9

The ratio of Lia’s books to Ali’s books is 6 : 9. Notice the writing order of the ratio. Can the ratio of Ali’s books to Lia’s books be stated 6 : 9? Why?

Mathematics for Junior High School Year 7 / 177

Problem 1

To make a cup of coffee, 2 teaspoons of coffee and 3 teaspoons of sugar are needed. Find the ratio of the coffee to the sugar to make a cup of coffee.

If you want to make 2 cups of coffee, how much sugar and coffee do you need? Find the ratio of the coffee to the sugar to make two cups of coffee. Can you find the ratio of the coffee to the sugar to make 5 cups of coffee? Without counting how much coffee and sugar that you need, can you find the ratio of the coffee to the sugar to make 10 cups of coffee? Regardless of how many cups of coffee you will make, can you find the ratio of the coffee to the sugar that you need? Suppose now to make a cup of coffee-milk a teaspoon of coffee and two teaspoons of milk powder are needed. Can you find the ratio of the coffee to the milk to make 6 cups of coffee-milk, 10 cups of coffee-milk, and 100 cups of coffee-milk?

Problem 2
Pak Imam has 5 sheep and 2 cows. Find the ratio of: a) sheep to cows. b) The number of sheep’s legs to the number of cows’ legs. Discussion Are both answers the same? Why ?

178 / Student’s Book - Proportion

Work together

Count how many boys and girls are in your class. Complete the table below: Boys Girls All students Answer the following questions. What is the ratio of the boys to the girls? What is the ratio of the girls to the boys? Are both ratios the same? Why? What is the ratio of the boys to all? What is the ratio of the girls to all? A ratio can be written in a simple fraction.

Mathematics for Junior High School Year 7 / 179

1.

Levi has 2 oranges, 4 apples, 4 tomatoes and 2 bananas. The ratio of oranges to apples is 2 : 4 or 1 : 2. Write the ratio of any fruits to each other.

2. The price of a pencil is Rp 1,000.00

The price of a pen is Rp 1,500.00 The ratio of the price of a pencil to the price of a pen is . ........ The price ratio of 5 pencils to 5 pens is .........
3. A mathematics book has 124 pages, while a bahasa Indonesia

book has 96 pages. The ratio of the pages of the mathematics book to those of the bahasa Indonesia book is ...... : ..... or ....... (simplify to) ........ The ratio of pages of 7 mathematics books to those of 7 bahasa Indonesia books is ......
4.

A rectangle has the width of 8 cm and the area of 104 cm2. The length of the rectangle is ...... cm. The ratio of the length to the width is .......... .

5.

Give the ratio of the number of vowels to the number of consonants in the alphabet. Vowels in the alphabet are a, e, i, o, u; so, there are 5. Consonants in the alphabet are ....................................................; there are ..... .

180 / Student’s Book - Proportion

The ratio of the number of vowels to the number of consonants is ........... . 6. Determine the ratio of number of vowels to the number of consonants of your name. 7. Agus is 12 years old. His sister, Diah, is 4 years old. His mother is 36 years old. Write the age ratio of Diah to Agus and that of Agus to his mother. 8. Two squares have the length of 5 cm and 9 cm each. Find the ratio of: a) their lengths b) their perimeters c) their areas

9. Critical Thinking: Determine the ratio of the length to the perimeter of a square. 10. Data of cattle in Central Kalimantan in 1991 according to the Center of Statistical Bureau.

Write the ratio of the cattle in Central Kalimantan Province in 1991.
cow = sheep

Cow Buffalo Goat Sheep Pig

49,500 8,800 16,000 1,200 121,400
..

....... .......

.... .... sheep .... = pig ....
buffalo = goat

Critical Thinking : Can you determine the ratio of the number of
legs of the cattle above.

Mathematics for Junior High School Year 7 / 181


								
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