116. How to check the correctness of a gas bill. The cost of gas in a city is 85 cents per 1000 cubic feet. According to his gas bill, the reading of Mr. Young's meter on Jan. 7 was 46,300. A month later it was 52,800. Hence, the amount of gas used during the month was 52,800-46,300, or 6500, cubic feet.

TO THE PEOPLES GAS LIGHT & COKE CO., DR.

Thus, to find the amount of gas used within a certain time, one notes the reading of the meter at the end of that time and subtracts from that amount the reading taken at the beginning. The result gives the number of cubic feet of gas used during the intervening time.

To find the cost proceed as follows: On Feb. 7, the reading is 52,800 cu. ft. On Jan. 7, the reading is 46,300 cu. ft.

Hence the number of cubic feet

of gas consumed = 6500 cu. ft.

At $.85 per M., the gas bill for the

month amounts to

6500

$

X.85)=$(6.500X.85) = $5.52

1000

Computation:

6.500

.85

32500

52000

5.52500

The decimal point is fixed by adding the number of places in the decimals of the factors. It may also be determined by estimating: Since 6X.8 is 4.8, or approximately 5, the decimal point should be placed after the 5.

The product is 5.52500, or 5.52, the last three figures being dropped.

10. In a certain city, the gas company supplies gas at 90 cents per 1000 cubic feet. Find the cost of gas used by four different consumers if the readings of their meters were as shown in the table below. Arrange the work as shown above.

11. Make a sketch of a gas meter whose reading shows 43,500 cubic feet.

117. Measuring electricity. Electricity is measured by means of electric meters in terms of watt hours (W.H.) and in kilowatt hours (K.W.H.).

1000 watts = 1 kilowatt

The dials of an electric meter (Fig. 223) are like those of the gas meters. They show, respectively,

thousands, hundreds, tens, and units. The divisions of the dials from right to left

denote 1 kilowatt hour, 10 kilowatt hours, 100 kilowatt hours, and 1000 kilowatt hours. When reading the meter one must first note the direction in which each pointer is turning and then the figure just passed over by the pointer. Thus the meter (Fig. 223) reads 3457 kilowatt hours. Why?

000

3

77

4

6

5

3/3

FIG. 223

4

EXERCISES

1. State the reading of each of the following electric meters (Figs. 224 and 225):

2. Make a sketch of the dials of a meter showing a reading of 6875 kilowatt hours.

12

10

USES OF THE CIRCLE IN GRAPHICAL
REPRESENTATION

LIBRARY

PENSIONS

TUBERCULOS13 300.

STATE

14%

THE CITY GETS ONLY 17%CENTS OUT OF EACH DOLLAR, ABOUT TH OF THE MONEY WITH WHICH TO DO APPROXIMATELY 2/3 OF THE WORK.

FIG. 226

118. How to read circular graphs. The picture (Fig. 226) represents graphically the distribution of the taxpayers' money in one of our large cities (Chicago) so that one may see at a glance how the money has been divided. The various amounts are represented as parts of the interior of a circle. This is an excellent device for comparing any item with each of the others and with the sum of all. Such a graphical device is called a circular graph.