2nd Quarter Summative Test in Math 9

The cost c varies directly as the number n of pencils is written as

• c = kn

• k = cn

• n = k/c

• c = k/n

The number of men (m) required to do a certain job varies inversely as the number of hours (h) required to do the job. Using k as the constant variation, what is the equation for this variation?

• A. m = k/h

• B. m = kh

• C. m = h + k

• D. m = h/k

Which is an example of a direct variation?

• xy = 10

• y = 2/x

• y = 5x

• 2/y = x

What happens to T when h is doubled in the equation T = 4h?

• T is halved

• T is tripled

• T is doubled

• T becomes zero

The pressure (P) of a gas varies directly as its temperature (t) and inversely as its volume (V). This relationship is written as

• P = kt/V

• P = kV/t

• P = ktV

• V = kt/p

What is the constant variation k if y varies directly as x and y = 21 when x = 7?

• A. 7/3

• B. 3/7

• C. k = 3

• D. k = 7

y varies directly as x and y = 48 when x = 3. Find the constant variation.

• A. 8

• B. 16

• C. 20

• D. 36

When y varies directly as x, what is true of the variables x and y?

• A. x and y increase together

• B. as x increases, y decreases

• C. x and y remain constant

• D. x and y cannot be determined

W varies jointly as a and c and inversely as b. This relationship is written as

• W = kac/2b

• W = kac/b

• W = kab/c

• w = kb/ac

Which is an example of an inverse variation?

• xy = 10z

• y = 2/x

• y = kx

• 2/y = x