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ENGINEERING ECONOMY (2)

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____________________________
- it is the analysis and evaluation of the factors that will affect the
success of engineering projects to the end that a recommendation
be made which will ensure the best use of capital.
____________________________
- it is an economic or a market situation in which only a single
seller or producer supplies a commodity or a service.
____________________________
- it is a market situation in which there are so few suppliers of a
particular product that one supplier’s actions significantly impact
prices and supply.
____________________________
- it is a market condition in which a product is traded freely by
buyers and sellers in large numbers without any individual
transaction affecting the price.
____________________________
- it is an economic or market situation in which a single consumer
or buyer buys a commodity or a service from suppliers.
____________________________
- It is an economic or market situation in which there are many
sellers or producers that supplies a commodity or a service to very
few consumers.
____________________________
- it is an economic system based on the private ownership of the
means of production and distribution of goods, characterized by a
free competitive market and motivation by profit.
____________________________
- these are tangible things – things that you can touch – that
satisfy human wants.
____________________________
- these are activities that people do for themselves or for other
people to satisfy their wants.
____________________________
- products or services that are required to support human life and
activities, which will be purchased in somewhat the same quantity
even though the price varies considerably.
____________________________
- products or services that are desired by humans and will be
purchased if money is available after the required necessities have
been obtained.
____________________________
- the quantity of a certain commodity that is bought at a certain
price at a given place and time.
____________________________
- the quantity of a certain commodity that is offered for sale at a
certain price at a given place and time.
____________________________
- under conditions of perfect competition the price at which a given
product will be supplied and purchased is the price that will result in
the supply and the demand being equal.
____________________________
- when the use of one of the factors of production is limited, either in
increasing cost or by absolute quantity, a point will be reached
beyond which an increase in the variable factors will result in a less
that proportionate increase in output.
Simple Interest
- interest on an investment that is calculated once per period,
usually annually, on the amount of the capital alone and not on
any interest already earned.
____________________________
- a type of simple interest in which interest is calculated as through
each month had 30 days.
Simple Interest
I = Pin
F = P + I = P + Pin = P(1 + in)
where:
I = simple interest
P = present worth
i = interest per period
n = number of interest period
Problem No. 1
Determine the ordinary simple interest on P5000 for 9 months and 10 days if the rate of
interest is 12%.
Problem No. 2
Determine the future worth on the previous problem.
Problem No. 3
If P1000 accumulates to P1500 when invested at a simple interest for 3 years, what is the
rate of interest?
Problem No. 4
Jojo bought a 2nd hand DVD player and then sold it to Rowace at a profit of 40%. Rowace
then sold the DVD player to Kat at a profit of 20%. If Kat paid 2856 more than it cost Jojo,
how much did Jojo pay for the unit?
____________________________
- it is a type of simple interest in which interest is calculated on the
basis of a year with 365 days rather than the conventional 360
days.
i = r/365 (for ordinary year)
= r/366 (for leap year)
I = Pin
F = P + I = P + Pin = P(1 + in)
where:
I = simple interest
P = present worth
i = interest per period
n = number of interest period
Problem No. 5
The exact simple interest of P5000 invested from June 21, 1995 to December 25, 1995 is
P100. What is the rate of interest?
Problem No. 6
Calculate for the exact simple interest on P15,000 for the period from February 12, to
August 15, 2004 if the rate of simple interest is 12%.
Rate of Discount
- is the discount of one unit of principal per unit time
𝑑
r=
1−𝑑
where:
r = rate of interest
d = rate of discount
Problem No. 7
A college freshman borrowed P2000 from a bank for his tuition fee and promised to pay
the amount for one year. He received only the amount of P1920 after the bank collected
an advance interest of P80. What was the rate of discount?
Problem No. 8
Ms. Evilla borrowed money from a bank. She receives from the bank P1340 and promised
to pay P1500 at the end of 9 months. Determine the corresponding discount rate or often
referred to as the banker’s discount.
Nominal Rate of Interest (r)
- is defined as the basic annual rate of interest.
r = im
where:
i = interest per period
m = number of interest per periods per year
m = 1 (annually)
= 2 (semi-annually)
= 4 (quarterly)
= 6 (bi-monthly)
= 12 (monthly)
= 52 (weekly)
= 360 (daily)
Effective Rate of Interest (ERI)
- is defined as the actual or exact rate of interest
earned on the principal during one-year period.
π‘Ÿ
𝐸𝑅𝐼 = 1 +
π‘š
π‘š
−1
Problem No. 9
What is the effective rate of interest corresponding to 18% compounded daily? Take 1 year
= 360 days.
Problem No. 10
What rate of interest compounded annually is the same as the rate of interest of 8%
compounded quarterly?
Problem No. 11
Which of these gives the lowest effective rate of interest?
a. 12.35% compounded annually
c. 12.20% compounded quarterly
b. 11.90% compounded semi-annually
d. 11.60% compounded monthly
Compound Interest
𝑛
π‘Ÿ
=𝑃 1+
π‘š
π‘šπ‘‘
−𝑛
π‘Ÿ
=𝐹 1+
π‘š
−π‘šπ‘‘
𝐹 =𝑃 1+𝑖
𝑃 =𝐹 1+𝑖
Continuously Compounding
π‘Ÿπ‘›
𝐹 = 𝑃𝑒
𝑃 = 𝐹𝑒 −π‘Ÿπ‘›
Single Payment Present Amount Factor
= (1 + i)-n
Single Payment Future Amount Factor
= (1 + i)n
Problem No. 12
A loan for P50000 is to be paid in 3 years at the amount of P65000. What is the effective
rate of money?
Problem No. 13
An amount of P1000 becomes P1608.44 after 4 years compounded bimonthly. Find the
nominal interest.
Problem No. 14
How long will it take money to double itself if invested at 5% compounded annually?
Problem No. 15
By the condition of a will, the sum of P20000 is left to a girl to be held in trust fund by her
guardian until it amounts to P50000. When will the girl receive the money if the fund is
invested at 8% compounded quarterly?
Problem No. 16
If the nominal interest rate is 5% percent, how much is P3000 worth in 15 years in a
continuously compounded account?
____________________________
- is defined as a series of equal payments occurring at equal interval of
time.
____________________________
- is a type of annuity where the payments are made at the end of each
period beginning from the 1st period.
1+𝑖 𝑛−1
𝐹=𝐴
𝑖
1− 1+𝑖
𝑃=𝐴
𝑖
−𝑛
uniform series compound amount factor =
uniform series sinking fund factor =
1+𝑖 𝑛 −1
𝑖
𝑖
1+𝑖 𝑛 −1
uniform series capital recovery factor =
uniform series present worth factor =
𝑖
1− 1+𝑖 −𝑛
1− 1+𝑖 −𝑛
𝑖
Problem No. 17
What annuity is required over 12 years to equate with a future amount of P20000?
Assume I = 6% annually.
Problem No. 18
How much money must you invest today in order to withdraw P2000 annually for 10 years
if the interest rate is 9%?
____________________________
- is a type of annuity where the payments are made at the
beginning of each period starting from the 1st period.
1− 1+𝑖
𝑃=𝐴
𝑖
−𝑛
1+𝑖
Problem No. 19
Mr. Ayala borrows P100,000 at 10% effective annual interest. He must pay back the loan
over 30 years with uniform monthly payments due on the first day of each month.
____________________________
- is the type of annuity where the first payment is made later
than the first or is made several periods after the beginning of
the annuity.
1− 1+𝑖
𝑃=𝐴
𝑖
−𝑛
1+𝑖
−𝑑
Problem No. 20
A person buys a piece of lot for P100,000 down payment and 10 deferred semi-annual
payments of P8,000 each, starting three years from now. What is the present value of the
investment if the rate of interest is 12% compounded semi-annually?
____________________________
- is a series of disbursements or receipts that increases or
decreases in each succeeding period by constant amount.
Problem No. 21
The Texas Highway Department expects the cost of maintenance for a particular piece of
heavy equipment to be P5000 in year 1, P5500 in year 2 and amounts increasing by P500
through year 10. At an interest rate of 10% per year, the present worth of the
maintenance cost is
Uniform Geometric Gradient
- is a series consisting of end-of-period payments, where each
payment increases or decreases by a fixed percentage
Problem No. 22
The first year maintenance cost for a new automobile is estimated to be P10,000 and it
increases at a uniform rate of 10% per year. Using an 8% interest rate, calculate the
present worth of cost of the first 5 years of maintenance.
____________________________
- refers to the present worth of a property that is assumed to
last forever. The capitalized cost of any property is the “sum of
the first cost and the present costs of perpetual replacement,
operation and maintenance”.
Case 1: No replacement, only maintenance
A
CC = FC +
i
Case 2: No maintenance, only replacement
P
CC = FC +
1+i n−1
Case 3: With maintenance and replacement
A
𝑃
CC = FC + +
𝑛
i
1+𝑖
−1
Problem No. 23
At 6%, find the capitalized cost of a bridge whose cost is P250M and life is 20 years, if the
bridge must be partially rebuilt at a cost of P100M at the end of each 20 years.
Problem No. 24
An equipment is purchased for P50,000. If the annual maintenance cost is P1500,
determine the capitalized cost of perpetual service with an interest rate of 6%.
____________________________
- is the decrease in the value of physical property due to
passage of time.
d = annual depreciation
C0 = first cost
BV = book value before life expectancy (L)
n = years before life expectancy (L)
SV = salvage value
Dn = total depreciation after year n
dn = depreciation charge on year n
____________________________
𝐢0 − 𝑆𝑉
𝑑=
𝐿
𝑛
𝐷𝑛 = 𝑛𝑑 = 𝐢0 − 𝑆𝑉
𝐿
𝐡𝑉𝑛 = 𝐢0 − 𝐷𝑛
Problem No. 25
An engineer bought a machine for P500,000. Other expenses including installation
amounted to P30,000. At the end of its estimated useful life of 10 years, the salvage value
will be 10% of the first cost. Using straight line method of depreciation
a) what is the annual depreciation?
b) what is the book value after 5 years?
Problem No. 26
A printing equipment costs P 73,500 has a life expectancy of 8 yrs. and has a salvage value
of P 3500 at the end of its life. The book value at the end of “x” years is equal to P 38,500.
Using straight line method of depreciation, solve for the value of “x”.
____________________________
𝐢0 − 𝑆𝑉 𝑖
𝑑=
1+𝑖 𝑛−1
1+𝑖 𝑛−1
𝐷𝑛 = 𝑑
𝑖
Problem No. 27
A broadcasting corporation purchased equipment for P53,000 and paid P1,500 for freight
and delivery charges to the job site. The equipment has a normal life of 10 years with a
trade-in value of P5,000 against the purchase of new equipment at the end of the life.
Using sinking fund method, (assume annual interest of 6%)
a) Determine the annual depreciation.
b) Determine the total depreciation after 5 years.
____________________________
π‘˜ =1−
𝐿
𝑛 𝐡𝑉𝑛
𝑆𝑉
=1−
𝐢0
𝐢0
𝐡𝑉𝑛 = 𝐢0 1 − π‘˜
𝑛
= 𝐢0
𝑆𝑉 = 𝐢0 1 − π‘˜ 𝐿
𝑑𝑛 = π‘˜πΆ0 1 − π‘˜ 𝑛−1
𝑆𝑉
𝐢0
𝑛ࡗ
𝐿
Problem No. 28
A VOM has a current selling price of P400. If the selling price is expected to decline at a
rate of 10% per annum due to obsolence,
a) what will be its selling price after 5 years?
b) what will be the salvage value if the life expectancy is 10 years?
Problem No. 29
A machine worth P250,000 has an estimated life of 15 years with a book value of P30,000
at the end of the period.
a) Determine the rate of depreciation.
b) Determine the book value after 10 years.
c) Determine the depreciation charge during the 10th year.
____________________________
𝐡𝑉𝑛 = 𝐢0
2
1−
𝐿
2
2
𝑑𝑛 = 𝐢0 1 −
𝐿
𝐿
𝑆𝑉 = 𝐢0
2
1−
𝐿
𝑛
𝑛−1
𝐿
Problem No. 30
An asset has a 1st cost of P22,000, an estimated life of 30 years. Using the double declining balance
method,
a) Determine the book value after 6 years.
b) Determine the depreciation charge during the 6th year.
c) What is the salvage value?
____________________________
𝑑𝑛 = 𝐢0 − 𝑆𝑉
𝐿−𝑛+1
π‘†π‘Œπ·
𝐿 𝐿+1
π‘†π‘Œπ· =
2
𝑛 2𝐿 − 𝑛 + 1
𝐷𝑛 = 𝐢0 − 𝑆𝑉
2
π‘†π‘Œπ·
Problem No. 31
An asset is purchased for P120,000. Its estimated economic life is 10 years, after which it
will be sold for P12,000. Using SOYD
a) find the depreciation charge during the 3rd year.
b) find the total depreciation after 3 years
____________________________
- is a certificate of indebtedness of a corporation usually for a
period not less than ten years and guaranteed by a mortgage on
certain assets of the corporation or its subsidiaries
πΉπ‘Ÿ
𝑃=
1− 1+𝑖
𝑖
−𝑛
+𝐢 1+𝑖
where:
F = face, or par, value
C = redemption or disposal price (often equal to F)
r = bond rate per period
n = number of periods before redemption
i = investment rate per period
P= value of the bond n periods before redemption
−𝑛
Problem No. 32
A man wants to make 14% nominal interest compounded semi-annually on a bond
investment. How much should he be willing to pay now for a 12%, P10,000- bond that will
mature in 10 years and pays interest semi-annually?
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