Q: X varies directly with y and z x equals 40 when y equals 10 and z equals 20 Find x when y equals 30 and z equals 40?

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x = 5.y.z so 5.10.12 = 600

m = 24

The answer is x=10. If: x=20 y=8 z=4 then: y=8/2=4 z=4*2=8 since x varies directly with y, meaning whatever happens to y, happens to x, so if y was divided by 2, then x should be divided by 2. After all, the inverse of division is multiplication.

y varies directly as x so y = cx for some constant c. y = 125 when x = 25 so 125 = c*25 so that c = 5 ie the relationship is y = 5x Then when x = 2, y = c*x = 5*2 = 10

xy = is a constant (k) so k = -360. When y = - 36, x = 10

Related questions

40

y = -5

1

y = 8

x = 5.y.z so 5.10.12 = 600

m = 24

50

y = kx: 10 = 37k so k = 10/37 and y = 10x/37

We write y=kx since y varies directly as x. Now we know if x is 5, y is 10. so we write 10=5k so k=2

The answer is x=10. If: x=20 y=8 z=4 then: y=8/2=4 z=4*2=8 since x varies directly with y, meaning whatever happens to y, happens to x, so if y was divided by 2, then x should be divided by 2. After all, the inverse of division is multiplication.

x = 75

y = x/k so 15 = 6/k making k = 0.4. when x = 10 y = 10/0.4 ie 25 alternatively y/x = k ie 15/6 = k so k = 2.5; y/10 = 2.5 making y = 25.