Business Mathematics for Social Science

  1. x is party constant and partly varies as y. When y = 2, x = 30, and when y = 6, x = 50

  2. Find the relationship between x and y

  3. Find x when y = 3

Solution:
Solution:

X is partly constant and partly varies as y"

—> x = ky + p

Where k and p are constant.

when y=2,x=30 —> 30 = 2k + p

when y=6,x=50 —> 50 = 6k + p

subtract: 20 = 4k

k = 5

sub back in the first: 30 = 10+p

p = 20

x = 5y + 20

notice this is just a variation of y = mx + b.

x = c + k y

Solving the two equation below simultaneously, we have:

30 = c + 2k

50 = c + 6k

---------------------subtract

-20 = -4k

k = 5

so 30 = c + 10

c = 20

x = 20 + 5 y or y = x/5 -4

and if y = 3 then

x = 20 + 5×3 = 20+15 = 35

x = 35 Ans.