Question

Y varies jointly as x and z. y=90 when x = 6 and z=3. Find y when x = 7 and z=4.
y =

Answer 1

To find the value of y when x = 7 and z = 4, we can set up a proportion using the given information:

y/xz = k

where k is the constant of variation.

Plugging in the values y = 90, x = 6, and z = 3, we have:

90/(6*3) = k

Simplifying, we find:

90/18 = k

5 = k

So the equation representing the relationship is:

y = 5xz

Now, we can substitute x = 7 and z = 4 into the equation to find y:

y = 5(7)(4)

y = 140

Therefore, when x = 7 and z = 4, y = 140.

Answer 2

y = 140

Explanation:

given that y varies jointly as x and z , then the equation relating them is

y = kxz ← k is the constant of variation

to find k , substitute y = 90 when x = 6 and z = 3 into the equation

90 = k × 6 × 3

90 = 18k ( divide both sides by 18 )

5 = k

y = 5xz ← equation of variation

when x = 7 and z = 4 , then

y = 5 × 7 × 4 = 140