Basic HTML Version
Q
uantitative
R
easoning &
P
roblem
S
olving
184
© 2014 Pacific Crest
Step
Explanation
5.
Determine the
form for the
solution
How does the writer of the problem description want you to present the
answer?
The number of mobile phones in 2020.
6.
Simplify the
problem
Identify logical subdivisions of the problem that match up with processes/
solutions you are already familiar with.
1) Determine the rate at which the number of phones increases each year.
2) Determine the model for the number of phones, a certain number of years after 2000.
7. Model each sub-
problem
Precisely translate each sub-problem into mathematical expressions, using
mathematical conventions.
1) Determine the rate at which the number of phones increases each year from the
year 2000 to the year 2008.
110 million to 270 million mobile phones in 8 years
(270 million phones) (110 million phones)
8 years
160 million phones
8 years
r
r
−
=
=
2) Determine the linear model for the number of phones after a number of years
n
=
b
+
r
×
y
(in millions of phones).
8.
Integrate the
sub-problems
Using mathematical reasoning, sequentially solve each of the sub-problems
leading to the final desired solution. Remember to observe both clarity and
neatness in your process and presentation!
1)
160 million phones
8 years
r
=
=
20 million phones per year
2)
n
=
b
+
r
×
y
(in millions of phones)
n
= 110 + 20 ×
y
In year 2020,
y
=
20
n
= 110 + 20 × 20 = 110 + 400 =
510 (in millions)
9.
Present the
solution
Present the solution in the required form (as stated in Step 5).
There will be 510 million mobile phones in the U.S. in 2020