Both x and y vary directly with each other and when x is 10, y is 14, which of the following is not a possible pair of corresponding values of x and y
(a) 25 and 35
(b) 35 and 25
(c) 35 and 49
(d) 15 and 21

Solution:

Given that x = 10 and y = 14 then as per the rule of direct proportion we have:

x/y = k

Where k = constant of proportionality

k = 10/14

k = 5/7

Verifying the alternatives given above we have:

(a) 25/35 = 5/7

(b) 35/25 = 7/5

(c) 35/49 = 5/7

(d) 15/21 = 5/7

Hence the pair which does not give the proportionality constant k = 5/7 is 35 and 25

✦ Try This: Both x and y vary inversely with each other and when x is 5, y is 4, which of the following is a possible pair of corresponding values of x and y? (a) 10 and 2, (b) 7 and 3, (c) 4 and 8, (d) 5 and 6

Given that x = 5 and y = 4 then as per the rule of direct proportion we have:

x ∝ 1/y

Which means

xy = k

Where k = constant of proportionality

k = 5 × 4

k = 20

Verifying the alternatives given above we have:

(a) 10 × 2 = 20

(b) 7 × 3 = 21

(c) 4 × 8 = 32

(d) 5 × 6 = 30

Hence the pair which gives the proportionality constant k = 20 is 10 and 2

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

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NCERT Exemplar Class 8 Maths Chapter 10 Problem 16

Both x and y vary directly with each other and when x is 10, y is 14, which of the following is not a possible pair of corresponding values of x and y (a) 25 and 35, (b) 35 and 25, (c) 35 and 49, (d) 15 and 21

Summary:

Both x and y vary directly with each other and when x is 10, y is 14, the pair which does not correspond to the pair of x = 10 and y = 14 is (35 and 25)

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☛ Related Questions:

• If x = 5y, then x and y vary ______ with each other
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• When two quantities x and y are in _______ proportion or vary ______ they are written as x ∝ y