Variations IGCSE 607

y is proportional to x and y=30 when x=6.

Find a formula for y in terms of x.

• $y=5x$

• $y=\frac{5}{x}$

• $y=\frac{x}{5}$

• $x=5y$

y varies directly with x, when y=40, x=5.

Find the value of y when x=20

• y= 16

• y=2.5

• y=160

• y= 25

y varies as the cube of x. Find the value of x when y=  $\frac{4}{3}$   given that when x=3, y= 4.5

• 8

• 4

• 2

• 6

y is directly proportional to  $\left(x+3\right)^2$ When x is 5, y is 16. Find the value of x when y=9

• x=36

• x= 8

• x=4

• x=3

What is the meaning of $v\propto\frac{1}{\sqrt{t}}$  

• y varies as the square root of t

• v varies inversly with the square root of t

• y varies as the inverse of the square root of t

• t varies as the square of v

The number of men,M, is inversely proportional to the number of women, W. When M=10, W=5. Find an expression of M in terms of W

• $M=\frac{50}{W}$

• $M=50W$

• $W=\frac{M}{50}$

• $W=\frac{50}{M}$

The time it takes to drive to Dallas is inversely proportional to your driving speed. It takes 3 hours to get to Dallas if you drive 96 km/h. How long will the trip take if you drive 116 km/h? (with 2d.p.)

• 2.5 hours

• 2.6 hours

• 2.4 hours

• 3.6 hours

• 3.5 hours

Boyle's Law states that the pressure, P, of a gas multiplied by its volume, V, is equal to a constant. Does this show direct variation, inverse variation, or neither?

• direct variation

• inverse variation

• neither

If f varies inversely as q², and f = 6 when q = 4 , find q when f = 24

• 4

• 2

• 6

• 3

The time it takes to drive to Dallas is inversely proportional to your driving speed. It takes 3 hours to get to Dallas if you drive 96 km/h. Write the expression that relates the time and the speed.

• $t=288s$

• $t=\frac{32}{s}$

• $t=\frac{288}{s}$

• $t=32s$

• $t=\frac{s}{32}$