A credit card charges a nominal interest rate of 19.5% per year, compounded quarterly. Find the effective annual rate EAR in percent.
r = 19.5%m = 4
EAR = %
2.Time value of moneyHard
You save €200 at the end of every month for 25 years. The account pays 3.6% per year, compounded monthly. How much have you saved at the end? Find FV.
A = €2003.6% / 12N = 300
FV = €
3.NPV & IRRMedium
A project costs €60 000 today and returns €18 000, €14 500, €26 000, €17 500, €22 500, €16 500 at the end of years 1 to 6. The cost of capital is 12%. Assume cash flows arrive evenly through each year. Find the discounted payback period DPB in years.
A project costs €50 000 and returns €33 000, €18 500, €23 000 at the end of years 1 to 3. Find its internal rate of return IRR in percent.
CF0 = −50 000CF1 = 33 000CF2 = 18 500CF3 = 23 000
IRR = %
5.Bond pricing & yieldMedium
A bond with a face value of €1 000 pays a 2% annual coupon in two half-yearly payments and matures in 3 years. The yield to maturity is 5% per year. Find the price P of the bond.
F = €1 000coupon = 2%YTM = 5%n = 3
P = €
6.Bond pricing & yieldHard
A bond trades at €940 with a yield to maturity of 3% (annual compounding) and a Macaulay duration of 6.4 years. Use the modified duration to estimate the new price P if the yield rises by 100 basis points.
P0 = €940y = 3%D = 6.4Δy = +100 bp
P = €
7.CAPM & WACCMedium
A company has equity worth €5 000 000 and debt worth €2 000 000. Its WACC is 11.03%, its pre-tax cost of debt is 4.5% and the tax rate is 20%. Find the cost of equity re.
A company's shares have a beta of 1.5 at its current debt-to-equity ratio of 0.25. It plans to raise its debt-to-equity ratio to 1.25. The tax rate is 28%, the risk-free rate 1.5% and the market risk premium 4%. Find the cost of equity re after the change.
Find the sample standard deviation s of the data: 38, 16, 55, 45, 22, 47, 37.
n = 7
s =
10.Descriptive statisticsHard
A quantity is normally distributed with mean 500 and standard deviation 50. What proportion P of values is below 400?
μ = 500σ = 50x = 400
P =
11.ProbabilityMedium
A bag holds 3 red and 6 blue balls. You draw two balls without putting the first one back. What is the probability P that both are red?
3 / 6
P =
12.ProbabilityHard
A test has 12 multiple-choice questions. A student who guesses gets each one right with probability 0.7, independently. What is the probability P of exactly 2 correct answers?
n = 12p = 0.7k = 2
P =
13.Normal distributionMedium
Drag z so that the shaded area between −z and z under the standard normal curve is 0.2586. Find z to two decimals.
A = 0.2586
z =
14.Normal distributionHard
Runner A's lap time X and runner B's lap time Y are independent and normal: X has mean 52 s and standard deviation 4 s, Y has mean 48 s and standard deviation 3 s. Find the probability P that X is greater than Y. Round z to two decimals.
μX = 52 s, σX = 4 sμY = 48 s, σY = 3 s
P =
15.Confidence intervalsMedium
The battery life of two phone models is compared. Model 1: 80 phones, mean 129 h, known standard deviation 20 h. Model 2: 80 phones, mean 135.5 h, known standard deviation 20 h. Find the margin of error E of the 95% confidence interval for μ₁ − μ₂.
The population standard deviation is 33. How large a sample n do you need so that a 99% confidence interval for the mean has a margin of error of at most 1?
σ = 33E = 199%
n =
17.Hypothesis tests & confidence intervalsMedium
The mean of a population is claimed to be 120; the population standard deviation is known to be 18. A random sample of 36 observations has a mean of 112.86. Test H₀: μ = 120 against H₁: μ ≠ 120. Find the p-value p.
μ₀ = 120σ = 18n = 36x̄ = 112.86H₁: μ ≠ μ₀
p =
18.Hypothesis tests & confidence intervalsHard
A one-sided z test at α = 0.05 must detect a shift of the mean of 3 units with a power of 95%. The standard deviation is 7. Find the minimum sample size n.
α = 0.05power = 95%δ = 3σ = 7zα = 1.645zβ = 1.645
n =
19.Linear regression & correlationMedium
The table gives 6 paired observations of x = advertising spend in k€ and y = sales in k€. Find the coefficient of determination r² of the least-squares line.
n = 6
r² =
20.Linear regression & correlationHard
The table gives 6 paired observations of x = car age in years and y = price in k€. Use the least-squares line ŷ = a + b·x. A new observation (3.5, 18) is made. Find its residual e = y − ŷ.
n = 6(3.5, 18)
e =
3Solutions
1.Time value of money
Answer: EAR = 20.97 %
Time value of money: money today is worth more than the same amount later, because it can earn interest. With interest rate i per period, an amount grows as FV = PV·(1 + i)n. A series of equal payments (an annuity) is valued by adding up each payment, which gives the annuity formulas.
Rate per period
r/m = 0.195/4 = 0.04875
Compound over one year
EAR = (1 + 0.04875)4 − 1 = 1.21 − 1 = 20.97%
Answer
EAR = 20.97%
The EAR is always above the nominal rate when interest compounds more than once a year.
2.Time value of money
Answer: FV = 97086 €
Time value of money: money today is worth more than the same amount later, because it can earn interest. With interest rate i per period, an amount grows as FV = PV·(1 + i)n. A series of equal payments (an annuity) is valued by adding up each payment, which gives the annuity formulas.
You paid in €60 000 yourself; the rest is interest.
3.NPV & IRR
Answer: DPB = 4.215 years
Payback period: the time until the cumulative cash flows repay the initial investment. Cash is assumed to come in evenly during each year, so the last part is a fraction of a year. The simple payback ignores the time value of money; the discounted payback period uses the discounted cash flows instead.
Discounted and cumulative cash flows
year 1: 18 000/1.12 = 16 071.43 → Σ = 16 071.43
year 2: 14 500/1.254 = 11 559.31 → Σ = 27 630.74
year 3: 26 000/1.405 = 18 506.29 → Σ = 46 137.03
year 4: 17 500/1.574 = 11 121.57 → Σ = 57 258.59
year 5: 22 500/1.762 = 12 767.10 → Σ = 70 025.70
Fraction of the last year
DPB = 4 + 2 741.41/12 767.10 = 4.215
Answer
DPB = 4.215 years
The discounted payback is always longer than the simple payback (3.086 years).
4.NPV & IRR
Answer: IRR = 25.02 %
Net present value: discount every cash flow back to today with the required rate of return r, then add them up: NPV = Σ CFₜ/(1 + r)ᵗ. A project with NPV > 0 earns more than r and adds value. The internal rate of return (IRR) is the rate at which NPV = 0.
Bracket the IRR
NPV falls as the rate rises, so the IRR lies between a rate with positive NPV and one with negative NPV.
NPV(25%) = 16.00
NPV(30%) = −3 199.82
Narrow down
Linear interpolation gives a first estimate; repeating it (or a calculator's IRR function) gives the exact rate.
IRR ≈ 25 + 5·16.00/(16.00 − (−3 199.82)) = 25.02%
exact: NPV(25.02%) = 0 → IRR = 25.02%
Answer
IRR = 25.02%
5.Bond pricing & yield
Answer: P = 917.4 €
Bond pricing: a bond’s price is the present value of its cash flows, discounted at the yield to maturity (YTM): the coupons form an annuity and the face value is paid back at maturity. P = C·(1 − (1 + y)⁻ⁿ)/y + F/(1 + y)ⁿ. When the yield is above the coupon rate the bond trades below face value, and the other way round.
Per period
C = €10.00, i = 0.025, N = 6
Present value of the coupons
€10.00·(1 − 0.8623)/0.025 = €55.08
Present value of the face value
€1 000·0.8623 = €862.30
Price
P = €917.38
Answer
P = €917.38
The yield is above the coupon rate, so the bond sells at a discount.
6.Bond pricing & yield
Answer: P = 881.6 €
Duration: the Macaulay duration is the weighted average time at which a bond pays its cash flows, with the present values of the cash flows as weights: D = Σ t·PVₜ/P. The modified duration D/(1 + y) estimates the percentage price change for a small change in yield: %ΔP ≈ −Dmod·Δy.
Modified duration
Dmod = 6.4/1.03 = 6.214
Estimated price change
%ΔP ≈ −6.214·(0.01) = −6.214%
P ≈ 940·(1 − 0.06214) = €881.59
Answer
P = €881.59
Duration is a linear estimate; for large yield changes convexity makes the true price a little higher.
7.CAPM & WACC
Answer: re = 14 %
Cost of capital: CAPM gives the return shareholders require: re = rf + β·(rm − rf). The weighted average cost of capital mixes equity and debt by their market values: WACC = E/V·re + D/V·rd·(1 − T), with V = E + D. Interest is tax-deductible, hence the (1 − T).
Weights
V = €7 000 000, E/V = 0.7143, D/V = 0.2857
Debt part of the WACC
0.2857·4.5%·(1 − 0.2) = 1.029%
Cost of equity
re = (11.03% − 1.029%)/0.7143 = 14%
Answer
re = 14%
8.CAPM & WACC
Answer: re = 11.16 %
Levered beta (Hamada): debt makes equity riskier. βL = βU·(1 + (1 − T)·D/E), where βU is the beta of the business without debt. To move a beta to another capital structure, unlever it first and then relever it at the new D/E.
Unlever the beta
βU = 1.5/(1 + 0.72·0.25) = 1.271
Relever at the new D/E
βL = 1.271·(1 + 0.72·1.25) = 2.415
Cost of equity (CAPM)
re = 1.5% + 2.415·4% = 11.16%
Answer
re = 11.16%
9.Descriptive statistics
Answer: s = 13.87
Descriptive statistics: the mean is the sum divided by n; the median is the middle value of the sorted data (the average of the two middle values when n is even). The sample standard deviation is s = √(Σ(x − x̄)²/(n − 1)). A z-score z = (x − μ)/σ says how many standard deviations a value lies from the mean.
Descriptive statistics: the mean is the sum divided by n; the median is the middle value of the sorted data (the average of the two middle values when n is even). The sample standard deviation is s = √(Σ(x − x̄)²/(n − 1)). A z-score z = (x − μ)/σ says how many standard deviations a value lies from the mean.
Standardise
z = −2
Standard normal table
Φ(−2) = 0.02275
P = 0.02275
Answer
P = 0.02275
11.Probability
Answer: P = 0.08333
Probability: with equally likely outcomes, P(A) = favourable/total. For independent events multiply: P(A and B) = P(A)·P(B). The complement often helps: P(at least one) = 1 − P(none). Binomial: in n independent trials with success probability p, P(X = k) = C(n, k)·pᵏ·(1 − p)ⁿ⁻ᵏ.
First and second draw
P = 3/9 · 2/8 = 6/72 = 0.08333
Answer
P = 0.08333
12.Probability
Answer: P = 0.000191
Probability: with equally likely outcomes, P(A) = favourable/total. For independent events multiply: P(A and B) = P(A)·P(B). The complement often helps: P(at least one) = 1 − P(none). Binomial: in n independent trials with success probability p, P(X = k) = C(n, k)·pᵏ·(1 − p)ⁿ⁻ᵏ.
From an area back to z: Φ(z) is the area to the left of z. For a left-tail area A, find z with Φ(z) = A in the table. A right-tail area A means Φ(z) = 1 − A. A central area A between −z and z leaves (1 − A)/2 in each tail, so Φ(z) = (1 + A)/2. For a value x, use x = μ + zσ.
Area to the left of z
Φ(z) = (1 + 0.2586)/2 = 0.6293
Read the z-table backwards
Find 0.6293 inside the table and read off z.
z = 0.33
Answer
z = 0.33
14.Normal distribution
Answer: P = 0.7881
Sums and differences of normal variables: if X and Y are independent and normal, X + Y and X − Y are normal too. Means add or subtract: E(X ± Y) = μX ± μY. Variances always add, also for a difference: Var(X ± Y) = σX² + σY², so σ = √(σX² + σY²). Standard deviations never add directly. The total of n independent items with the same distribution has mean n·μ and standard deviation σ·√n. Then standardise as usual: z = (x − mean)/σ and read Φ(z).
Distribution of the difference
μ = 52 − 48 = 4 s, σ = 5 s
Standardise
z = (0 − 4)/5 = −0.8
Probability
P = 1 − Φ(−0.8) = 0.7881
Answer
P = 0.7881
15.Confidence intervals
Answer: E = 6.198 h
Interval for a difference: estimate ± critical value × standard error. For two independent means with known σ: SE = √(σ₁²/n₁ + σ₂²/n₂) and z. With equal unknown variances: pooled s_p and t with n₁ + n₂ − 2 degrees of freedom. For paired data, work with the differences: d̄ ± t·s_d/√n.
Point estimate
x̄₁ − x̄₂ = 129 − 135.5 = −6.5
Standard error
SE = √(20²/80 + 20²/80) = 3.162
Margin of error
E = 1.96·3.162 = 6.198
Answer
E = 6.198 h
The interval does not contain 0, so the means differ significantly.
16.Confidence intervals
Answer: n = 7227
Confidence interval for a mean: x̄ ± margin of error. With a known population σ the margin is z·σ/√n; with only the sample standard deviation s, use t with n − 1 degrees of freedom: t·s/√n. Critical values: z = 1.645 (90%), 1.96 (95%), 2.576 (99%). To get a margin E or smaller, you need n ≥ (z·σ/E)², rounded up.
Solve for n
n = (2.576·33/1)² = 7226
Round up
A sample size is a whole number, and rounding down would make the margin too large.
n = 7227
Answer
n = 7227
17.Hypothesis tests & confidence intervals
Answer: p = 0.01731
Hypothesis test: the test statistic = (estimate − value under H₀)/(standard error under H₀). The p-value is the probability, assuming H₀ is true, of a statistic at least as extreme as the one observed: the area in one tail for a one-sided H₁, twice the tail area for a two-sided H₁. Reject H₀ when p ≤ α.
Test statistic
SE = σ/√n = 18/√36 = 3
z = (112.86 − 120)/3 = −2.38
Tail area
Φ(2.38) = 0.9913
1 − Φ(2.38) = 0.0087
p-value
p = 2·0.0087 = 0.01731
Answer
p = 0.01731
p ≤ 0.05, so H₀ is rejected at the 5% level.
18.Hypothesis tests & confidence intervals
Answer: n = 59
Sample size for a test: to detect a true shift δ with power 1 − β in a one-sided z test at level α, the standard error must satisfy δ = (z_α + z_β)·σ/√n, so n = ((z_α + z_β)·σ/δ)², rounded up.
Solve for n
n = ((1.645 + 1.645)·7/3)² = 58.93
Round up
n = 59
Answer
n = 59
19.Linear regression & correlation
Answer: r² = 0.9387
Least-squares regression: with x̄ and ȳ the means, Sxx = Σ(x − x̄)², Syy = Σ(y − ȳ)² and Sxy = Σ(x − x̄)(y − ȳ), the line ŷ = a + b·x has slope b = Sxy/Sxx and intercept a = ȳ − b·x̄, so it always passes through (x̄, ȳ). Pearson's correlation coefficient r = Sxy/√(Sxx·Syy) lies between −1 and 1; r² is the fraction of the variation in y explained by the line.
Means
x̄ = 21/6 = 3.5
ȳ = 248/6 = 41.33
Sums of squares and products
Sxx = Σ(x − x̄)² = 17.5
Sxy = Σ(x − x̄)(y − ȳ) = 74
Syy = Σ(y − ȳ)² = 333.3
Coefficient of determination
r² = 74²/(17.5·333.3) = 0.9387
Answer
r² = 0.9387
About 93.87% of the variation in y is explained by the line.
20.Linear regression & correlation
Answer: e = −4.667
Least-squares regression: with x̄ and ȳ the means, Sxx = Σ(x − x̄)², Syy = Σ(y − ȳ)² and Sxy = Σ(x − x̄)(y − ȳ), the line ŷ = a + b·x has slope b = Sxy/Sxx and intercept a = ȳ − b·x̄, so it always passes through (x̄, ȳ). Pearson's correlation coefficient r = Sxy/√(Sxx·Syy) lies between −1 and 1; r² is the fraction of the variation in y explained by the line.