Answers to
Questions About Numbers
Mathematics Teacher, March 1986
1. Gold alloys used to make jewelry are measured by a symbol such as 18K, indicating the
karats. What number is used as a measure of the karats for pure gold?
24K
2. In the musical time signature "3 over 4," the "3" indicates three beats to each measure.
What does the 4 indicate? A quarter note gets one beat.
3. An example of a Social Security number is 123-45-6789. What special information is
provided by the first three digits? They identify the particular office issuing the card.
These area numbers are assigned according to the zip code used on the application. However, area numbers prior to 1972 were assigned according to state.
4. The number 4 is significant in naming a female horse. A filly is a female horse less than 4
years old. What is the name given to a female horse more than 4 years old? Mare.
5. Relative humidity is given as a percentage, such as 45%. The percentage gives the ratio of
what two measurements? The amount of water vapor in the air and the amount required for saturation.
6. Many American spacecraft have names ending with a numeral, such as Apollo 15. The first
six American spacecraft with humans aboard had different names, but all the names
ended with the same numeral. What was that numeral? 7.
7. One of the numbers used to describe photographic film is an ASA number, such as ASA 100
or ASA 200. What does the ASA number indicate? Larger ASA numbers indicate that the film is faster, which means it reacts more quickly to light and needs less exposure.
8. The size of a shotgun is given in terms of its gauge. What is the meaning of "12 gauge?" It takes 12 lead balls, each the size of the bore, to weigh one pound.
9. The pH number is used to discuss acid rain and to indicate whether soil is acidic or alkaline.
A neutral solution that is neither acidic nor alkaline has what pH number? 7. These numbers are based on a logarithmic scale.
10. In human beings, each cell (except egg and sperm cells) contains how many chromosomes? 46.
11. New air conditioners ordinarily have a tag with an EER rating, such as "8.0 EER." EER stands
for Energy Efficient Ratio, so that 8.0 should be interpreted as the ratio 8.0 to 1. What
does each of the two numbers in the ratio represent? Cooling capacity in BTUs per hour and the watts of electricity used.
12. On many ships, time is signaled by the ship's bell. What is the significance of eight bells? Signals the end of each four-hour watch.
13. A hurricane has wind speeds of 75 mph and above. What is the name given to winds with
wind speeds of 25 — 31 mph? Strong breeze. The General wind classifications are
Calm, Light air, Light breeze, Gentle breeze, Moderate breeze, Fresh breeze, Strong breeze, Moderate gale, Fresh gale, Strong gale, Whole gale, Storm, and Hurricane.
14. An amateur rugby team (rugby union) consists of how many players who start? 15.
15. Oil production is generally measured in barrels. One barrel of oil contains how many liters
(or gallons)? 159 liters (42 gallons).
16. Passenger ships are usually measured in terms of gross tonnage, which is a measure of
volume rather than weight. What does it mean to say the gross tonnage of a ship
is 20 000? The volume of the enclosed space is 20 000 in units of 100 cubic feet.
17. The specific heat of water is 1. What is the meaning of a specific heat of .5 for a substance? It only takes .5 calories of heat to raise the
temperature of 1 gram of the substance 1 degree Celsius.
18. In adults, cholesterol levels under 200 are generally considered desirable. What does a cholesterol level of 200 mean? 200 mg of cholesterol per 100 cc of plasma.
19. Historically, one way of measuring the brightness of a star was in terms of magnitude, for example, first magnitude, second magnitude, and so on. A star of first magnitude is
approximately how many times as bright as a star of second magnitude? 2.5.
20. The solar constant is a unit used to describe the amount of solar energy hitting the top of
the earth's atmosphere. It is defined as the number of calories received per square centimeter in one minute. The solar constant has a value equal to approximately how many calories?
2.