Given, n varies directly as m
∴ n ∝ m
∴ n = km …(i) where, k is the constant of variation
i. When m = 3, n = 12
∴ Substituting m = 3 and n = 12 in (i), we get n = km
∴ 12 = k × 3
∴ k = 12/3
∴ k = 4
Substituting, k = 4 in (i), we get n = km
∴ n = 4m …(ii)
This is the equation of variation.
ii. When m = 6.5, n = ?
∴ Substituting, m = 6.5 in (ii), we get n = 4m
∴ n = 4 × 6.5
∴ n = 26
iii. When n = 28, m = ?
∴ Substituting, n = 28 in (ii), we get n = 4m
∴ 28 = 4m
∴ m = 28/4
m = 7
iv. When m = 1.25, n = ?
∴ Substituting m = 1.25 in (ii), we get n = 4m
∴ n = 4 × 1.25
∴ n = 5
| m |
3 |
5 |
6.5 |
7 |
1.25 |
| n |
12 |
20 |
26 |
28 |
5 |
