It is given that l varies directly as m.
(i) Write an equation which relates l and m.
(ii) Find the constant of proportion (k), when l is 6 then m is 18.
(iii) Find l, when m is 33.
(iv) Find m when l is 8.
Solution:
(i) When l varies directly as m one can write
l ∝ m
l = km
Where k = positive constant of proportionality
l/m = k
(ii) k = l/m
k = 6/18
k = 1/3
(iii) k = l/m
k = 1/3
1/3 = l/m
1/3 = l/33
l = 33/3
l = 11
(iv) k = 1/3
k = l/m
1/3 = l/m
1/3 = 8/m
m = 8 × 3
m = 24
✦ Try This: It is given that l varies inversely as m.
(i) Write an equation which relates l and m.
(ii) Find the constant of proportion (k), when l is 12 then m is 4.
(iii) Find l, when m is 6.
(iv) Find m when l is 24.
(i) When l varies inversely as m one can write
l ∝ 1/m
lm = k
Where k = positive constant
(ii) k = lm
k = 12 × 4
k = 48
(iii) k = lm
k = 48
48 = lm
48 = 6l
l = 48/6
l = 8
(iv) k = 48
k = lm
k = 24m
24m = 48
m = 48/24
m = 2
☛ Also Check: NCERT Solutions for Class 8 Maths Chapter 13
NCERT Exemplar Class 8 Maths Chapter 10 Problem 71
It is given that l varies directly as m. (i) Write an equation which relates l and m. (ii) Find the constant of proportion (k), when l is 6 then m is 18. (iii) Find l, when m is 33. (iv) Find m when l is 8
Summary:
Given that l varies directly as m.(i) the equation which relates l and m is l/m = k(ii) The constant of proportion k = 1/3 when l is 6 then m is 18.(iii) l = 11 when m is 33.(iv) m = 24 when l is 8
☛ Related Questions:
- If a deposit of Rs 2,000 earns an interest of Rs 500 in 3 years, how much interest would a deposit o . . . .
- The mass of an aluminium rod varies directly with its length. If a 16 cm long rod has a mass of 192 . . . .
- Find the values of x and y if a and b are in inverse proportion:a. 12 x 8 b. 30 5 y
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