Quiz 3
1
1. If 𝑧 varies jointly as 𝑥 and 𝑦, and 𝑧 = 4 and when 𝑥 = 2 𝑎𝑛𝑑 𝑦 = 16, 𝑓𝑖𝑛𝑑 𝑧 𝑤ℎ𝑒𝑛 𝑥 =
12 𝑎𝑛𝑑 𝑦 = 8.
a. 84
b. 48
c. 32
d. 64
2. If 𝑝 varies jointly as square of 𝑥 and the fourth root of 𝑦, and 𝑃 = 24 and when 𝑥 =
12 𝑎𝑛𝑑 𝑦 = 16, 𝑓𝑖𝑛𝑑 𝑝 𝑤ℎ𝑒𝑛 𝑥 = 24 𝑎𝑛𝑑 𝑦 =
a.
b.
c.
d.
256
16
.
48
12
24
96
3. Ohm’s law states that the current I in a direct-current circuit varies inversely as the
resistance R. If a resistance of 6 ohms produces a current of 1.5 amperes, find the current
when resistance is 0.2 ohms.
a. 45 A
b. 0.05 A
c. 450 A
d. 90 A
4. The pressure of wind on a wall varies jointly as the area A of the wall and square of the
velocity 𝑣 of the wind. If 𝑃 = 20 𝑝𝑜𝑢𝑛𝑑𝑠 𝑤ℎ𝑒𝑛 𝐴 = 40 𝑠𝑞𝑢𝑎𝑟𝑒 𝑓𝑒𝑒𝑡 𝑎𝑛𝑑 𝑣 =
20 𝑚𝑖𝑙𝑒𝑠 𝑝𝑒𝑟 ℎ𝑜𝑢𝑟 , 𝑓𝑖𝑛𝑑 𝑝 𝑖𝑓 𝐴 = 60 𝑠𝑞𝑢𝑎𝑟𝑒 𝑓𝑒𝑒𝑡 𝑎𝑛𝑑 𝑣 = 16 𝑚𝑖𝑙𝑒𝑠 𝑝𝑒𝑟 ℎ𝑜𝑢𝑟.
a. 48
b. 12.8
c. 0.8
d. 19.2
5. The weight w of an object on or above the surface of the earth varies inversely as the
square of the distance d of the object from the center of the earth. If an astronaut weighs
90 pounds at the surface of the earth, how much would she weigh in a satellite 200 miles
above the surface? (Radius of the earth 4000 miles).
a. 90 Ibs
b. 82 Ibs
c. 99 Ibs
d. 110 Ibs
6. The volume V of a given mass gas varies directly as the temperature T and inversely as
the pressure P. If a gas has volume 8 cubic inches when the temperature is 160 degree
Quiz 3
Kelvin and the pressure is 150 pounds per square inch, find the volume when the
temperature is 200 degree Kelvin and the pressure is 30 pounds per inch.
a. 8
b. 50
c. 5
d. 12
7. If 𝑧 varies as directly with 𝑥 and inversely with the square of 𝑦, and 𝑧 = 4 and when 𝑥 =
1
4
a.
𝑏.
𝑎𝑛𝑑 𝑦 = 8, 𝑓𝑖𝑛𝑑 𝑥 𝑤ℎ𝑒𝑛 𝑧 = 4 𝑎𝑛𝑑 𝑦 = 4.
1
c.
8
1
d.
16
3
32
5
16
8. If 𝑝 varies jointly as square root of 𝑥 and the square root of 𝑦, and 𝑃 = 4 and when 𝑥 =
9
16 𝑎𝑛𝑑 𝑦 = 9, 𝑓𝑖𝑛𝑑 𝑝 𝑤ℎ𝑒𝑛 𝑥 = 36 𝑎𝑛𝑑 𝑦 = 4.
a. 3
b. 1.5
c. 4
d. 8
9. Ohm’s law states that the current I in a direct-current circuit varies inversely as the
resistance R. If a resistance of 8 ohms produces a current of 2.5 amperes, find the current
when resistance is 0.5 ohms.
a. 40
b. 10
c. 8
d. 20
10. The pressure of wind on a wall varies jointly as the area A of the wall and square of the
velocity 𝑣 of the wind. If 𝑃 = 10 𝑝𝑜𝑢𝑛𝑑𝑠 𝑤ℎ𝑒𝑛 𝐴 = 20 𝑠𝑞𝑢𝑎𝑟𝑒 𝑓𝑒𝑒𝑡 𝑎𝑛𝑑 𝑣 =
10 𝑚𝑖𝑙𝑒𝑠 𝑝𝑒𝑟 ℎ𝑜𝑢𝑟 , 𝑓𝑖𝑛𝑑 𝑝 𝑖𝑓 𝐴 = 30 𝑠𝑞𝑢𝑎𝑟𝑒 𝑓𝑒𝑒𝑡 𝑎𝑛𝑑 𝑣 = 8 𝑚𝑖𝑙𝑒𝑠 𝑝𝑒𝑟 ℎ𝑜𝑢𝑟.
a.
b.
c.
d.
48
1.2
9.6
96