Direct and Indirect ( Inverse) Proportion_ Day 1

Hope you still remember the past lesson.

Proportion

​Let's Recall

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Multiple Choice

True or False

$$\frac{6}{12}\ =\ \ \ \frac{1}{3}$$  

• False

• True

• Partly true

• Partly false

Draw

Find the unknown number: $$\frac{6}{n}\ =\ \ \ \frac{3}{4}$$  

Draw

Find the unknown number: $$\frac{5}{4}\ =\ \ \ \frac{a}{36}$$  

Multiple Choice

Find the missing term.

$$\frac{18}{20}=\frac{9}{n}$$  

• n =2

• n = 10

• n = 12

• n = 15

​Did you Know That...

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An African elephant eats 100 to 200 kilograms of plats every day and species about 16 hours eating every day ​.

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What will happen if the elephants eats more plants?​

​https://en.wikipedia.org/wiki/African_elephant

​Did you Know That...​

An African elephant eats 100 to 200 kilograms of plats every day and species about 16 hours eating every day ​.What will happen if the elephants eats more plants?​

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The more plants an elephant eats, the heavier it becomes​. We can say the food intake and the weight of the elephant are proportional.

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Poportion may either be ...​

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​https://en.wikipedia.org/wiki/African_elephant

Direct and Indirect (Inverse) Proportion

By Venus Daydayan

​INDIRECT OR

Sample Problem for Direct Proportion

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​If 8 students can clean 2 classrooms, then how many students can clean 5 classrooms?

Solutions: Set the two ratios students to classroom. Then,write the proportion

8 : 2 = n : 5​

​Method 1: " the product of the means = product of the extremes"

8 : 2 = n : 5

​ 2 x n = 8 x 5

2 n = 40​

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n = 20

Answer : 20 students​

​Method 2 : Use the fact that proportions are equal ratios

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Answer : 20 students​

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Sample Problem for Direct Proportion

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​If 8 students can clean 2 classrooms, then how many students can clean 5 classrooms?

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8 students can clean 2 classrooms, then 20 students can clean 5 classrooms.

This is a direct proportion because as the number of students increases, the number ​of classrooms increases also. More students are needed to clean more classrooms. Less students are needed to clean less classrooms.

Sample Problem for Indirect Proportion

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​If 4 painters can paint a house in 1 day, then how many days can 8 painters paint the same day?

Analysis: The more people to paint, the less time it would take them to finish the job.

4 painters x 1 day = 8 painters x n days

n = 4 ÷ 8​

n = 1 / 2​

The number of painters double in number; therefore, the time will be halved. it would take only 1/2 day for 8 men to paint the house.​

Sample Problem for Indirect Proportion

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Eight men have enough food for 20 weeks. How long will the food last for 10 men?

Solution: 8 men x 20 weeks = 10 men x n weeks

160​ = 10n

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n = 16​

​Answer : 16 weeks

The food is enough for 8 men in 20 weeks. If the number of men increases to 10, then the food will last for fewer weeks. The more people eating, the less time the food will last.

Multiple Choice

State whether each problem is an example of a direct or indirect proportion.

A car travelled 268 km every 4.5 hours. At this rate, how long would it take to travel 380 km?

• Direct Proportion

• Indirect Proportion

Multiple Choice

State whether each problem is an example of a direct or indirect proportion.

Jerry typed 182 words in 6 1/2 minutes. At that rate, how many words could be type in 13 minutes?

• Direct Proportion

• Indirect Proportion

Multiple Choice

State whether each problem is an example of a direct or indirect proportion.

If 7 men can do a certain job in 12 days, then how long would it take 6 men to do the same job?

• Direct Proportion

• Indirect Proportion

Multiple Choice

State whether each problem is an example of a direct or indirect proportion.

Three boys can finish filling up a tank of water in 2 hours. how long will 4 boys take to do the same job?

• Direct Proportion

• Indirect Proportion

Multiple Choice

State whether each problem is an example of a direct or indirect proportion.

Dr. Perez treats 24 patients in 3 days. How many patients does he treat in two weeks, if he goes to his clinic Monday to Saturday?

• Direct Proportion

• Indirect Proportion