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Using an Equation to Predict

Direct deposit. The percentage of workers receiving direct
deposit of their paychecks went from 32% in 1994 to 60%
in 2004 (www.directdeposit.com). Let 1994 be year 0 and
2004 be year 10.

a) Write the equation of the line through (0, 32) and
(10, 60) to model the growth of direct deposit.

b) Use the accompanying graph to predict the year in
which 100% of all workers will receive direct deposit
of their paychecks.

c) Use the equation from part (a) to predict the year in
which 100% of all workers will receive direct deposit.

I have a very hard time with these, I just never seem to get the correct.

Solution Preview

a)

Lines have the equation y = mx + b. The "m" is the slope of the line, and the "b" is the y-intercept. Let's find the slope first:

m = (60 - 32)/(10 - 0) = 28/10 = 2.8

Now we know the line looks like y = 2.8x + b. Let's solve for b. Pick ...

$2.19