# Ratio and proportion in geometry I

## Lesson details

### Key learning points

1. In this lesson, we will compare the side lengths of triangles, one of which is an enlargement of the other, and calculate the ratios of the lengths of corresponding sides.

### Licence

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## Video

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## Worksheet

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## Starter quiz

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### 5 Questions

Q1.
Fill in the gap: If two quantities are in the same ratio then there are _______ relationships I can use to find a missing value.
four
one
three
Q2.
Lots of the same groups of yellow and red counters are put in a bag. Fill in the missing value in the ratio table.
1.25
25
6.25
Q3.
Lots of the same groups of yellow and red counters are put in a bag. Fill in the missing value in the ratio table.
1.3
3.9
6
Q4.
Lots of the same groups of yellow and red counters are put in a bag. Fill in the missing value in the ratio table.
16.1
2.3
5
Q5.
Yellow and red counters are in the ratio 2 : 3. What fraction of the counters are yellow?
2/3
3/2
3/5

## Exit quiz

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### 5 Questions

Q1.
State the ratio between the side lengths AB and BC.
10 : 4
2 : 4
4 : 10
Correct answer: 4 : 2
Q2.
State the constant of proportionality between triangle ABC and triangle DEF.
2
3
4
Q3.
Find the length of side DE.
10cm
40cm
80cm
Q4.
Find the length DE.
20cm
25cm
80cm