Quiz in MATH 223 - Part 2

At 1:00 P.M., a thermometer reading 70°F is taken outside where the air temperature is -10°F (10 below zero). At 1:02 P.M., the reading is at 26°F. At 1:05 P.M., the thermometer is taken back indoors, where the air is at 70°F. What is the temperature reading at 1:09 P.M.?

• 56°F
• 65°F
• 44°F
• 60°F

The rate of population growth of a country is proportional to the number of inhabitants. If the population of a certain country now is 40 million and 50 million in 10 years time, what will be its population 20 years from now?

• 62.5 million
• 65.20 million
• 56.20 million
• 52.60 million

Radium decomposes at a rate proportional to the amount at any instant. In 100 years, 100 mg of radium decompose to 96 mg. How many mg will be left after 100 years?

• 88.60
• 95.32
• 92.16
• 90.72

A radioactive substance has a mass of 100 mg. After 10 years, it has decayed to a mass of 75 mg. What will the mass of the substance be after another 10 years?

• 56.25 mg
• 34.36 mg
• 49.34 mg
• 63.12 mg

The substance decomposed at a rate proportional to the amount present. What is the half life of the substance if 90% decomposes in 100 years?

• 568 years
• 465 years
• 658 years
• 586 years

If a culture of particular type of yeast, the amount active ferment doubles in 3 hours, how much active ferment in 15 hours?

• 32Q₀
• 101.82Q₀
• 45Q₀
• 107.5Q₀

The rate at which a chemical substance decomposes is proportional to the amount of the substance still unchanged. What is the proportionality constant if the amount of the substance changes from 1000 grams to 500 grams in 2 hours.

• – 0.897
• – 0.378
• – 0.347
• – 0.98

A radioactive element changes at a rate to the amount at any instant. How many grams of the element will be left in 300 years, if 100 grams was set aside 50 years ago and at present is only 90 grams?

• 48 grams
• 50 grams
• 23 grams
• 57 gram

A certain radioactive element dissipates at a rate proportional to its amount instantaneously present. If one-half of any given amount of the element dissipates in 1,600 years, what fraction will dissipate during the second century?

• 8.3 %
• 5.6 %
• 3.8 %
• 9.2 %

A bacterial population is known to have a rate of growth proportional to itself. If between noon and 2 P.M., the population triples, at what time, no controls being exerted, should the population becomes 100 times as what it was at noon?

• 8:23 PM
• 9:35 PM
• 9:35 PM
• 10:37 PM