A2 7.1 Direct and Inverse Variation

Which of the following represents direct variation?

• y = kx
• y = k/x
• y = x/k
• y = mx + b

Which of the following represents indirect variation?

• y = kx
• y = k/x
• y = x/k
• y = mx + b

 Y varies directly with x, and y is 84 when x is 16. Which equation represents this situation?

• y=1344x
• y=100x
• y=5.25x
• y=4/21x

If y = 15 when x = 12 find y when x = 32.

• 40
• -40
• 5
• -5

The width of a rectangle varies inversely with its length.  If the width is 6 when the length is 24, give an equation that shows the relationship.

• y = 4x
• y = 144x
• y = 4/x
• y = 144/x

Y is directly proportional to the square of z and inversely proportional to w.

• y=kz²/w
• y=kz/w
• y=w/kz²
• y=w/kz

The number of kilograms of water in a person’s body varies directly as the person’s mass.  A person with a mass of 90 kg contains 60 kg of water.  How many kilograms of water are in a person whose mass is 75 kg?

• 50 kg water
• 72 kg water
• 94 kg water
• 150 kg water

The interest received on a savings account varies directly with the amount deposited. Daniel received $55.35 in interest on $1230 he deposited. How much interest would Daniel have received if he had deposited $2000 into his account?

• 34.04
• 90.00
• 1,285.35
• 44,444.44

 Y varies inversely with x, and y is 0.5 when x is 4. Which equation represents this situation?

• y=2x
• y=2/x
• y=4x
• y=x/2

y varies directly with the square of x.  If y=40 when x=4, find y when x = 7

• 17.5
• 70
• 122.5