Question

Value of m varies directly as value of n and n=5 when m=12. What is n when m=18? plz explain

Answer 1

Value of m varies directly as value of n
m = kn

• n=5 when m=12

12 = k(5)
k = 12/5

• n = ? when m = 18

m = kn
18 = (12/5) × n
n = 18 × 5/12
n = 15/2
n = 7.5

Answer 2

Concept

One quantity directly changes in response to a change in another quantity, which is referred to as direct variation. This suggests that if one quantity increases, the other will follow suit and rise in proportion. In a similar manner, if one quantity declines, the other amount also declines. Since direct variation and variation are related in a linear way, the graph will be a straight line.

Given

n = 5 when m = 12

Find

we need to find the value of n when m is 18.

Solution

Since value of m varies directly as value of n.

Therefore, m = kn

given, n = 5 when m = 12

⇒12 = k(5)

k = 12/5

then, what is n when m =18

⇒m = kn

18 = (12/5) × n

n = 18 × 5/12

n = 15/2

n = 7.5

Therefore we get the value of n as 7.5 when m is 18.

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