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Parity Zetamac

Converting call to put and vice versa
Converting combo value to stock value
Converting straddle to call or put value and vice versa
Converting B/W or P+S to call or put value

About this drill · FAQ

Parity Zetamac is a Zetamac-style speed drill for put-call parity. Each question shows every value but one, and you type the missing price as fast as you can.

What it drills

  • Every question follows from one identity: C − P = S − K + r/c.
  • C is the call, P the put, S the stock, K the strike, and r/c the rate and carry to expiry.
  • Put-Call: given one option plus S, K and r/c, solve for the other option.
  • Combo: a combo is C − P, so you convert between the combo value and the stock price.
  • Straddle: a straddle is C + P, so you convert between the straddle and the call or put.
  • B/W and P+S: buy/writes and puts plus stock, quoted against the strike, converted to a call or put.

How scoring works

  • The default session is 120 seconds. Longer sessions are available on Pro.
  • A correct answer scores one point and the next question appears as soon as you type it.
  • There is no penalty for a wrong entry. You keep typing until the price is right.

What a good score is

  • Across 816 TraderPrep sessions at 120 seconds, as of September 2026, the median score is 6.
  • A score of 9 or more puts you in the top quarter of TraderPrep players.
  • A score of 13 or more puts you in the top tenth.

How to get faster

  • Memorise C = P + S − K + r/c and P = C − S + K − r/c so you never rearrange during a session.
  • Compute S − K first. It is the one piece shared by every category.
  • Learn B/W = P + r/c and P+S = C − r/c. They turn the last category into one subtraction.
  • Start with one category, then add the others once each one is automatic.

FAQ

Where is put-call parity used in interviews?
In options market-making interviews at firms like SIG and Optiver, where you quote options and convert between a call, a put and the stock on the spot. Parity is the arithmetic underneath every one of those conversions.
Is it free?
Yes. You get free plays every day at up to 120 seconds, and a TraderPrep account adds more. Pro unlocks unlimited plays and the longer sessions.
How is it different from the arithmetic Zetamac?
The arithmetic drill tests raw adding and multiplying. This one tests whether you can move between option prices without thinking about the formula.