Solve: If x varies inversely as y and x = 20 when y = 600, find y when x = 400.

Solution:

When x varies inversely as y then we can write:

x ∝ 1/y

x = k/y where k is a positive constant

xy = k

Given x = 20 and y = 600

xy = 20 × 600 = 12000

If x = 400 then the new value of y will be

400 × y = 12000

y = 12000/400

y = 30

✦ Try This: If x varies inversely as y and x = 50 when y = 120, find y when x = 80

When x varies inversely as y then we can write:

x ∝ 1/y

x = k/y where k is a positive constant

xy = k

Given x = 50 and y = 120

xy = 50 × 120 = 6000

If x = 80 then the new value of y will be

80 × y = 6000

y = 6000/80

y = 75

☛ Also Check: NCERT Solutions for Class 8 Maths Chapter 13

NCERT Exemplar Class 8 Maths Chapter 10 Problem 63

If x varies inversely as y and x = 20 when y = 600, find y when x = 400

Summary:

If x varies inversely as y and x = 20 when y = 600, the value of y = 30 if x = 400

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