Is delta additive or average?

CFA Level III
#1

Hey,

I just did the PM mock and got the question wrong about delta. I understand the 1 and the 0 as at expiration ones itm and ones otm. For all your positions to find net delta is it simply the sum of all of them or is it the average of them for the number of positions? It seemed in this case they just said itm long is 1 so delta is 1 for position but I just want to make sure.

Thanks.

#2

Additive. I got it wrong as well, took the average but when you think about it, just break it down in the long and short side. So if long position is ITM and short is OTM, then it’s just 1-0 = 1. Same as the payoff/profit formula, just add them up.