NCERT Figure it Out 11 - Karim and the genie - Algebra Play
Question: (i) How many coins did Karim start with if after three doubles-and-pay-8 he had exactly 8 left to pay? (ii) For what cost c per round does he finish with more than he started (starting from 7)? (iii) If he starts with n, what c leaves him with nothing after three rounds?
Answer: (i) 7 coins. (ii) Cost less than 7 per round. (iii) Charge 8n/7 coins per round.
Full step-by-step NCERT solution with diagrams on Something by Zero.