Can anyone please help decode how these 4 answers are so different in how they are providing the "minimum fuel required for the flight" value in the long text.
In answer 1 (128kg) [ignoring a round issues or is it] - it is just Flight Fuel (80) + Ballast Fuel (48) = 128kg or 129 (but no rounding seems to give this value)
Answer 2 it's 216kg ... but the same FF + BF (159+68) add to give 227 and NOT 216 ? ? ?
Answer 3 it's 159kg ... but the FF+BF (107+142 = 249) and NOT 159 like the answer
Answer 4 it's 114kg ... but the FF+BF (66+56=122) and NOT 114 like the answer

I'm good with all the other math and calculations and despite inconsistent rounding, think they're ok.
I've checked Errata and don't believe its listed. What am I missing please?
Original questions and answers provided. (questions from page 172 exercise 5.10 & answers on page 207 / 208)

Hi t117tim.

The answers in the current text book are the same as your copy.

For question no 1.
The fuel required at TAKE OFF is 80 kg plus 10% (contingency) plus 41kg (final reserve fuel) = 129 kg
While not asked, the fuel required at START UP is, 129 plus startup and taxy plus ballast fuel which is 129 plus 8 plus 48 equals 185 kgs.

The ballast fuel is not included in any fuel calculations other than what is put in the tanks.

Cheers W

Thank you @WayneJ much appreciated. That makes perfect sense (in hindsight).
[& book editors ... just the tiniest of substantiaons of every number in an answer to explain workings would really help people decode "the answer"].