The variable x varies directly as y and x = 80 when y is 160. What is y when x is 64?

Solution:

When x ∝ y then,

x/y = k, where k = +ve proportionality constant

When x = 80 y = 160

80/160 = k

k = 1/2

Therefore the new value of y when x = 64 is:

64/y =1/ 2

y = 64 × 2

y = 128

✦ Try This: The variable x varies directly as y and x = 40 when y is 120. What is y when x is 72?

When x ∝ y then,

x = ky

x/y = k

k = +ve proportionality constant

When x = 40 y = 120

40/120 = k

k = 1/3

Therefore the new value of y when x = 72 is:

72/y = 1/ 3

y = 3 × 72

y = 216

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

---

NCERT Exemplar Class 8 Maths Chapter 10 Problem 64

The variable x varies directly as y and x = 80 when y is 160. What is y when x is 64

Summary:

The variable x varies directly as y and x = 80 when y is 160. The value of y is 128 if x is 64

---

☛ Related Questions:

• l varies directly as m and l is equal to 5, when m = 2/3 . Find l when m = 16/3
• If x varies inversely as y and y = 60 when x = 1.5. Find x, when y = 4.5
• In a camp, there is enough flour for 300 persons for 42 days. How long will the flour last if 20 mo . . . .