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Grade 8 - Mathematics
2.14 Proportion - I

Two quantities are proportional if they have a same ratio or rate.

Proportion:

  • Two ratios set equal
  • Setting two fractions equal
  • Solved by cross multiplying
  • Direct or inverse
  • Example: a/b = c/d
    cross products ad =cd
    ad and cb are called the cross products of this proportion.
    The cross products of any proportion are equal.
  • the product of extremes in a proportion = the product of means in the proportion.
  • Cross products can be used to determine whether two ratios are in proportion.
Example:
3/2 = 9/x
cross products: 3x = 18
x = 6

Example:
q/25 = 52/100
cross products: q x 100 = 25 x 52
100q = 1300
q = 13


Directions: Answer the following questions. Also write at least ten examples of your own.
Q 1: The terms at the middle of a proportion are called ______.
Means
Center
Extremes

Q 2: If 2,5,10,x are in proportion then value of x = _____.
20
15
25

Q 3: a, b, c and d are four numbers if a:b = c:d then a, b, c and d are in ______.
Equation
Proportion
Ratio

Q 4: What are the extremes in 1:5 = 5:25.
2 and 23
1 and 25
3 and 15

Q 5: If 3,7,9,x are in proportion then value of x = ____.
21
17
18

Q 6: The product of ____ in a proportion = the product of means in the proportion.
Center
Means
Extremes

Q 7: The terms at the last of a proportion are called ______.
Opposites
Extremes
Means

Q 8: What are the means in 25:30 = 250:300.
12 and 112
30 and 250
42 and 75

Question 9: This question is available to subscribers only!

Question 10: This question is available to subscribers only!


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