H(a)=b means that a years after 1980, the percentage of U.S. households with Internet access was b %.
B
b
H(a)=b means that a years after 1980, the percentage of U.S. households with Internet access was b %.
C
c
H(a)=b means that a years after 1980, the percentage of U.S. households with Internet access was b %.
D
d
H(a)=b means that a years after 1980, the percentage of U.S. households with Internet access was b %.
A
a
In 2003, 23 year after 1980, 55 % of households had Internet access.
B
b
In 1984, 4 years after 1980, k % of households had Internet access.
C
c
In 2007, 27 years after 1980, at least 61 % of households had Internet access.
D
d
The sum of the percentages of households that had Internet access in 1997 and in 2001, 17 and 21 years after 1980, respectively, is approximately the same as the percentage of households that had Internet access in 2009, 29 years after 1980.
Practice makes perfect
a
Function notation is one way to write functions. It explicitly shows that y is a function of x.
f(x)=y
In the given situation we have that H(x)=y, where x is the number of years after 1980 and y is the percentage of U.S. households with Internet access. We will use this to explain the meaning of the given statement.
H(23)=55
Comparing this to H(x)=y, we can see that x=23 and y=55. Thus, the statement is telling us that 23 years after 1980, which is the year 2003, 55 % of households had Internet access.
b
The given statement is H(4)=k. Comparing this to H(x)=y, we can see that x=4 and y=k. Thus, the statement is telling us that in 1984 (4 years after 1980), k % of households had Internet access.
c
Let's consider the given statement.
H(27)≥ 61
Recall that H(x) represents the percent of U.S. households with Internet use x years after 1980. Therefore, the above statement tells us that this percentage 27 years after 1980 is greater than or equal to 61. This means that at least 61 % of U.S. households had Internet access in the year 2007.
d
Let's finally consider the last statement.
H(17)+H(21)≈ H(29)
Recall that H(x) represents the percent of U.S. households with Internet use x years after 1980. The above statement tells us that the sum of these percents in 1997 and in 2001, 17 and 21 years after 1980, respectively, is approximately the same as the percentage of households that had Internet access in 2009, 29 years after 1980.
