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Question
If C = kd
(i) what is the relation between C and d?
(ii) find k when C = 30 and d = 6
(iii) find C, when d = 10
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Solution
(i) Given C = kd
⇒ `"C"/"d"` = k
This is in the form `x/y` = k
As C increases d also increases
∴ It is direct proportion
(ii) When C = 30 and d = 6, k = `"C"/"d"`
= `30/6`
k = 5
(iii) When d = 6, C = 30 ...[from (ii)]
When d = 10, C = ?
`("C"_1)/("d"_1) = ("C"_2)/("d"_2)`
`30/6 = ("C"_2)/10` .......[When d = 10]
C2 = `(30 xx 10)/6`
C2 = 50
C = 50
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