Variations - JSS3 Mathematics Past Questions and Answers - page 1

1

If 𝑦 varies directly as 𝑥 and 𝑦=15 when 𝑥=3, what is 𝑦 when 𝑥=6?

A

30

B

45

C

15

D

18

correct option: a
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2

If 𝑦 varies inversely as 𝑥 and 𝑦=10 when 𝑥=5, what is 𝑦 when 𝑥=8?

A

6.25

B

4

C

12.5

D

25

correct option: a
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3

If 𝑧 varies jointly as 𝑥 and 𝑦, and 𝑧=24 when 𝑥=4 and 𝑦=3, what is 𝑧 when 𝑥=6 and 𝑦=5?

A

60

B

30

C

36

D

45

correct option: c
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4

If 𝑧 varies partly as 𝑥 and inversely as 𝑦, and 𝑧=10 when 𝑥=5 and 𝑦=2, what is 𝑧 when 𝑥=10 and 𝑦=4?

A

5

B

20

C

2.5

D

40

correct option: a
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5

If 𝑦 varies directly as 𝑥 and 𝑦=9 when 𝑥=6, find 𝑦 when 𝑥=12.

Given 𝑦=𝑘𝑥, substituting the given values:

9=𝑘⋅6

Solving for 𝑘:

𝑘=9/6=1.5

Now, find 𝑦 when 

x=12:

𝑦=1.5⋅12=18

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6

If 𝑦 varies inversely as 𝑥 and 𝑦=20 when 𝑥=4, find 𝑦 when 𝑥=5.

Given 𝑦=𝑘/𝑥, substituting the given values:

20=𝑘/4

Solving for 𝑘:

𝑘=20⋅4=80

Now, find 𝑦 when 𝑥=5:

𝑦=80/5=16

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7

If 𝑧 varies jointly as 𝑥 and 𝑦, and 𝑧=36 when 𝑥=3 and 𝑦=4, find 𝑧 when 𝑥=6 and 𝑦=2.

Given 𝑧=𝑘𝑥𝑦, substituting the given values:

36=𝑘⋅3⋅4

Solving for 𝑘: 𝑘=36/12

=3

Now, find 𝑧 when 𝑥=6 and 𝑦=2:

𝑧=3⋅6⋅2=36

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