Is my maths right, please?

I started planning out my next challenge - 100k words in 3 months.

Each chapter has 2 scenes of 1k words each so that's 2k words per chapter.

100÷2=50 chapters, right so far?

This next bit is where I need a bit of a confidence booster.  I wanna work out how many days it'll take to plan out the entire novel at 5 chapters a day, so:

50÷5=10 days, yeah?

I know it's simple maths, I've just never been confident with even the simplest maths is all so just wanna make sure I've got it right, unlike my JanNo novel where I was a chapter short.

Assuming I've got that right, the next bit is to work out how long it'll take me to write the novel.  My PB is currently 9k words on the final day of my JanNo novel, but that's so far off my norm which is about 5 or 6 chapters at 750 words per chapter for MG.

This is a YA novel and there are 2k words per chapter instead of 750, so I'm hoping to maybe write 3 chapters a day tops 'cos that's my usual speed when I'm in the writing zone.

Here comes a bit more maths:

50÷3=16.6, so lets round that up to 17 days... that can't be right though 'cos my PB was 50k in 12 days for NaNo and JanNo, so how am I going to squeeze out another 50k in less than a week?!?  Even my current PB is 9k in one day so how am I going to squeeze out a PB every single day for a week?

I is muchly confuzzled!

Anyone fancy helping me to work it out properly please?

See why I need your help now?  lol