Engineering Economy 6th Edition Solutions

Working Through Engineering Economy 6th Edition Solutions

The Blank and Tarquin textbook covers present worth, annual worth, future worth, rate of return, and depreciation methods across about twelve chapters. The solutions manual exists because the problems aren't trivial, and trying to reverse-engineer them from partial credit is frustrating. I'll walk through how the manual is structured, where most people run into trouble, and one specific edge case I actually hit. The solutions are organized by chapter. Each problem walks through the setup, the formula selection, the intermediate values, and the final answer. The thing people don't realize about this book is that the chapter problems often have multiple valid approaches. Chapter 4 on present worth has problems that can be solved using PW, AW, or FW and they should all give the same answer if you're doing it right. The solutions manual shows one path. That path isn't always the fastest, but it's the one the author considers standard. The manual assumes you have a financial calculator or spreadsheet software. A lot of the intermediate steps are skipped. If you're checking your work and your numbers don't match, the first thing to do is verify your cash flow diagram before you blame the solution manual.

How to Use the Solutions Effectively

Cover the answer first. Set up the problem. Draw your cash flow diagram with the direction of each arrow clearly marked. This takes about two minutes and catches more mistakes than anything else I've seen. Then plug into your chosen method. If you're using Excel, the functions you need are NPV, PV, FV, PMT, RATE, and IRR. The textbook problems mostly use uniform series, so PMT and PV are the workhorses. When the solution doesn't match, check three things in order: your interest rate period, whether you're using the correct compounding frequency, and whether you applied the factor correctly to the right time period. The most common error I see is treating an annual interest rate as if it applies to monthly cash flows without adjusting. That single mistake throws off everything downstream. The depreciation chapters especially require careful attention. MACRS uses the half-year convention by default, and the recovery periods are fixed by IRS tables. If a problem specifies a different convention, the solution manual will show it, but you have to read the problem statement carefully before you pull out a table. I lost about twenty minutes on a problem once because I blindly used the standard GDS table instead of reading that the asset was placed in service mid-quarter. The QBPS convention changes every quarter's depreciation fraction. Not something you want to discover after you've built your cash flow schedule.

Where People Get Stuck

Rate of return problems in chapters 7 and 8 are where most students fall apart. The textbook introduces incremental analysis for comparing mutually exclusive alternatives, and the solution manual presents it in a way that assumes you already understand why you're doing it. The trick is that you don't just pick the highest IRR. You order the alternatives by increasing initial investment, calculate the incremental cash flow between consecutive alternatives, and check whether the incremental IRR exceeds the MARR. If it does, you keep the higher-cost alternative. If it doesn't, you keep the lower-cost one. You repeat until you've compared every pair. Another blind spot is sensitivity analysis. The problems often ask you to show how the decision changes when a parameter shifts by plus or minus ten percent. Students will calculate one NPV and stop. The question wants a table or a graph. The solution manual does this in the later chapters but glosses over it in the earlier ones. Build the habit early. Spreadsheets help a lot here, but they also hide errors. I've had students turn in work where the formula referenced the wrong cell and the number looked reasonable enough to pass casual inspection. If you're using Excel for the manual's problems, cross-check at least one calculation by hand. Just one. It takes thirty seconds and it keeps you honest.

What the Manual Won't Tell You

The solutions assume clean data. Real problems have messy constraints. Tax effects, salvage value uncertainty, inflation adjustments across multiple years — the textbook treats these systematically, but the walkthroughs are idealized. When you encounter a problem that mixes inflation with after-tax cash flows, the manual may split the steps into separate sections. Read those sections in order because the real interest rate derivation depends on having already adjusted the nominal rate. There's also a quirk in the factor tables at the back of the book. They round to four decimal places. For most problems that's fine. For problems that ask you to verify a small difference between two alternatives, that rounding can flip your decision by a few dollars. If you need precision beyond the table values, use the formula or a calculator with more digits. The solution manual sometimes flags this but doesn't always explain it clearly.

Accessing the Solutions

The solutions are published alongside the textbook as a companion manual. You'll find them through academic publishers, university bookstores, or licensed educational platforms. Make sure you're matching the edition correctly. The 6th edition has different problem numbers and some different methodology explanations than the 5th and 7th. A common mistake is pulling solutions for the wrong edition and then wondering why your cash flow diagram doesn't align with the answer key. If you're working through this on your own without a course, start with Chapter 1 and 2. Those chapters establish the notation and the basic interest formulas. Skip ahead too quickly and you'll miss the foundation that every later chapter builds on. The later chapters on replacement analysis and capital budgeting are where the material gets practically useful, but they're also where the assumptions become unstated. Read the problem statements twice before you start calculating.